Encapsulated cure systems

ABSTRACT

Encapsulated cure systems are provided wherein a curative is incorporated into a solid or semi-solid carrier material whereby mere fracturing or failure of the capsule wall encapsulating such cure systems will not provide for or allow sufficient release of the curative. Also provided are adhesive systems incorporating said encapsulated cure systems.

This application is based upon and claims priority from U.S. ProvisionalPatent Application Nos. 60/606,720, DeBraal et. al., filed Sep. 1, 2004;60/665,134, DeBraal et. al., filed Mar. 25, 2005, and 60/692,008,DeBraal et. al, filed Jun. 17, 2005.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to adhesive and sealant compositions wherein oneor more of the reactive and/or curable or polymerizable constituents ofsaid compositions are encapsulated. It more particularly relates toencapsulated cure systems for, directly or indirectly, initiating and/oreffectuating the cure or polymerization of adhesive and sealantcompositions, as well as methods of making the same.

2. Description of Related Art

The use of microencapsulated ingredients in the manufacture ofpharmaceuticals, pesticides, paints, adhesives, sealants and printinginks is well known. Perhaps the most widely known use of microcapsuleshas been in the product generally referred to as carbonless paper whichincorporate or have applied thereto coatings comprisingmicroencapsulated inks and/or other color forming agents that arereleased upon the application of pressure to the paper surface. In themanufacturing and service sectors one of the most widely known use ofmicrocapsules has been in the manufacture of adhesives and sealants.Here the use of microencapsulation allows one to form a one-partadhesive or sealant from a typical two- or more-part adhesive andsealant system. Microencapsulation also allows one to pre-apply suchadhesives and sealants to substrates at the site of manufacture orconversion rather than at the site of use or installation. The use ofmicroencapsulation in adhesive and sealants is well known and takes manydifferent paths.

Encapsulated solvent-based adhesive systems are of several differentconstructs. Roesch et. al. (U.S. Pat. No. 5,922,798) teach solvent basedadhesive compositions wherein a solvent, alone or together with atherein dissolved resin, is encapsulated and used to bond twosubstrates, each of which is dissolved or softened by the solvent.Eichel (U.S. Pat. No. 2,907,682) discloses adhesive tapes wherein theadhesive portion comprises a combination of encapsulated solvent andencapsulated solid adhesives, which are soluble in the solvent. Uponapplication of the tape to a substrate and the further application ofpressure, the capsules rupture allowing the solvent to dissolve or atleast tackify the adhesive whereby, upon evaporation or absorption ofthe solvent, an adhesive bond is formed. Where the solvent isnon-evaporating, e.g., a plasticizer, and neither the substrate carryingthe adhesive nor the substrate to which it is to be bonded absorb thenon-volatile solvent, the result of the combination of the solvent andadhesive material is a pressure sensitive adhesive. Adhesives based onpolyvinyl acetate, rubber, nitrile rubber, ethyl cellulose, or othercellulose derivatives such as cellulose acetate are especially suitedfor the solvent activation/reactivation type application.

Hot melt adhesive systems employing encapsulated solvents are alsoknown. Baetzold et. al. (U.S. Pat. No. 6,084,010) teaches solid, tackyor non-tacky hot melt glue compositions having incorporated thereinmicrocapsules of a solvent capable of softening or further tackifyingthe hot melt. Rubbing the hot melt composition, typically in the form ofa stick, on the substrate to which it is to be applied fractures thecapsules, releasing the solvent which, in turn, softens the hot melt andallows it to be deposited on the surface of the substrate.

Another type of encapsulated adhesive and sealant is that where theadhesive or sealant material or, in the case of a curable adhesive orsealant material, the components thereof are encapsulated in a singlecapsule. These capsules are typically applied to a substrate in a bindersystem that is non-tacky and dry to the touch. In this way, otherwisetacky or liquid flowable adhesives can be pre-applied, but not activatedor bond forming until the capsule walls themselves are fracturedreleasing or exposing the adhesive materials. For example, Eichel (U.S.Pat. No. 2,986,477) teaches the encapsulation of tacky adhesivematerials. Wallace (U.S. Pat. No. 4,428,982) teaches the encapsulationof curable anaerobic adhesives wherein the encapsulating material is airpermeable so that the curable adhesive remains in a liquid or uncuredstate in the capsule until use. Schwantes (U.S. Pat. No. 6,592,990)teaches encapsulated adhesives, particularly pressure sensitiveadhesives, wherein the adhesive is formed in-situ, after encapsulationof the ingredients therefore.

A third, and perhaps the most common use of encapsulation in adhesivesand sealants, involves curable or reactive adhesive and sealantcompositions which rely upon the presence of curatives or curing and/orcross-linking agents and/or other reactants such as activators,catalysts, initiators, accelerators, and the like for effectingpolymerization or curing of the composition so as to form the desiredadhesive or sealant, wherein one or more of the reactive constituents isencapsulated so as to isolate it from the other constituents. Theseadhesive and sealant compositions may be of a number of different types:some of the more typical being those based on epoxies, urethanes,unsaturated polyesters, alkyds, and (meth)acrylates, as monomers,pre-polymers, and low molecular weight polymers or combinations thereof.Such adhesive and sealant compositions are more typically found in theform of and characterized as two or more part systems wherein the partsare combined by the applicator at the time of use. However, with theadvent of encapsulation technology, it is possible to encapsulate one ormore of the reactive constituents, isolating it from the otherconstituents, so as to produce storage stable, one-part adhesive andsealant compositions. For example, the curatives or curing and/orcross-linking agents and/or other reactants may be encapsulated and saidcapsules dispersed in the liquid polymerizable monomer which forms thematrix of the adhesive or sealant. Alternatively, the liquidpolymerizable component may be encapsulated and the curative or curingagent adhered to the outer wall of the capsule or the liquidpolymerizable component may itself be encapsulated as well.

Oftentimes these one-part adhesive and sealant compositions encompassseveral different microcapsules, each containing one of the curatives orcuring and/or cross-linking agents and/or other co-reactive constituentsalone or together with other constituents of the adhesive or sealantcomposition. For example, with a free-radical polymerizable adhesive orsealant composition, so long as the oxidizing agent (typically theperoxide) and the reducing agent (typically an amine and/or metallocene)are in separate capsules, the system is stable. Here two differentmicrocapsules may be employed wherein each contains a portion of thepolymerizable component and one or more of the aforementioned curingagents and/or co-reactants. Similarly, for co-reactive polymerizablesystems, each of the co-reactive species is encapsulated in separatemicrocapsules.

In the case of pre-applied adhesive and sealant compositions, typicallya liquid adhesive or sealant composition containing the encapsulatedcomponent(s) dispersed therein is applied to the substrate and a polymerfilm formed over and encasing the liquid adhesive or sealant on thesubstrate to which it is applied. The polymer film holds the liquidadhesive or sealant composition in place and forms a protective barrieras well as a dry to the touch surface for the adhesive or sealantcomposition. Here, however, the curable or polymerizable component ofthe adhesive or sealant is not present in an encapsulated form, i.e., isnot in the form of discrete microcapsules.

A second embodiment for the pre-applied adhesive and sealants is thatwhere one or more of the components of the adhesive or sealant,including, in particular, the liquid polymerizable components, isencapsulated in a plurality of microcapsules which are dispersed in aliquid curable, polymerizable, or hardenable binder system. In thisembodiment, one or more solid curative or curing agents or one or moresolid activators, catalysts, initiators, accelerators, and the like foreffecting curing or polymerization of the encapsulated liquidpolymerizable component may be dispersed in the binder, withoutencapsulation. Alternatively, all of the components of the adhesive orsealant composition may be encapsulated in a plurality of differentmicrocapsules which are dispersed in the liquid binder. In use, each ofthese modified binder systems is then applied to the intended substrateand allowed to cure, polymerize or harden; thereby binding themicrocapsules to the substrate surface. Suitable binder systems may ormay not co-react with the adhesive or sealant composition during cure orpolymerization of the same. Most often the binders do not co-react, butinstead act as a filler of the polymerizable or curable compositions.

Activation of these encapsulated adhesive and sealant compositions iseffectuated by crushing the microcapsules so that the liquidpolymerizable component comes into contact with the curative, curingagent, activator, catalyst, initiator, accelerator or the like. Mixingof the ingredients is reliant upon flow caused by the application ofpressure and/or relative movement of the substrates to be bonded. Thus,because of the limited mixing, it is important that such systems be asfluid as possible to maximize the opportunity for mixing. Higherviscosity materials will result in less mixing and, thus, only partialcuring of the curable materials. More importantly, higher viscositymaterials are more difficult, if not impossible, to encapsulate. Whereencapsulation is possible, particle size becomes an issue. Typically, inencapsulating high viscosity liquids, one tends to get a large number oflarge and small particles or microcapsules rather than a parabolicdistribution where large and small particles are few.

While the advent of such encapsulated adhesive and sealant compositionshas greatly broadened and/or simplified the end-use applications towhich such adhesive and sealant systems are employed, they are notwithout remaining shortfalls. Premature fracturing of the capsules isperhaps the most prevalent of issues, especially in situations where theadhesive or sealant is used in rapid industrial manufacturing processesrequiring quick delivery and application of the adhesive or sealant and,further, especially in the case of pre-applied adhesives or sealants,where the substrates to which the adhesives or sealants are pre-appliedare likewise subject to such manufacturing processes, repeated handlingor movement, etc. Concern for premature fracturing is not, however,limited to the application and use of the encapsulated adhesive. Such isalso a great concern in the storage and handling of the microcapsules aswell as the manufacture and processing of the adhesive or sealantitself, especially during incorporation of the encapsulated componentinto the matrix of the adhesive or sealant, or, in the case ofpre-applied adhesive, incorporation of the encapsulated adhesive systemsinto the binder materials. Concerns with premature fracturing areheightened with systems that are thixotropic, have a high viscosityand/or incorporate fillers, especially granular fillers and fillershaving sharp edges, or are subject to high shear mixing and dispensingprocesses.

Oftentimes to overcome concerns with premature fracturing, the thicknessof the microcapsule walls is increased. This is especially found withpre-applied adhesives and sealants, particularly thread-locking orthread-sealing pre-applied adhesives and sealants, respectively.Consequently, cell walls comprising as much as 30 weight percent ormore, more typically from 10% to 20% by weight, of the encapsulatedcomponent are not unusual in those one-part liquid systems to be appliedat the time of use or from 15% to 25%, by weight in the case ofpre-applied adhesives. However, as thicker and thicker walls areemployed, less and less curable material is available with the sameweight or volume of adhesive or sealant. Consequently, there is lesscurable material at the bond-line for forming the adhesive bond or seal.Because of the limited amount of curable material, there is poor flowand wetting of the substrate surfaces. Additionally, the large amount ofshell wall fragments creates a gap between two substrates to be mated,much like grains of sand between plates of glass, which gap may bedifficult to fill with the liquid curable material: again due to itslimited quantity and low viscosity.

Furthermore, as the wall thickness increases, it becomes more and moredifficult to break the cell walls when fracturing is desired. Thus,greater forces are needed to ensure the release of a comparable amountof the liquid curable or polymerizable component. Because rupture of thecapsules in these instances is typically as a result of finger or handpressure, pinch rollers and/or threading of threaded elements, thedegree of rupture of the microcapsules lessens as the thickness of thecapsule walls increases, especially if there is not a concurrentincrease in the amount of pressure applied. This is particularly so forapplications other than threading applications where multiple rotationsare employed. Consequently, depending upon the specific end-useapplication, there may be poor or low sealant or bond strength due tothe release of insufficient liquid curable or polymerizable components;thus, limiting performance or even the suitability of such materials fora given application. Similarly, as oftentimes found with the bondingand/or sealing of threaded elements, a larger volume of the pre-appliedadhesive or sealant is necessary in order to attain the same bond orseal volume of cured material arising from the use of liquid, as opposedto pre-applied, adhesive and sealant compositions.

In order to moderate the need for thicker and thicker capsule walls, itis also known to incorporate hollow microspheres as “spacer” particlesin the adhesive or sealant composition. For example, Hinterwaldner (U.S.Pat. No. 4,362,566) employs hollow microspheres to enhance storagestability of the adhesive formula as well as enhance fracturing of themicrocapsules during activation and application of the adhesivematerial. However, the addition of such microspheres adds yet anotheradditive to the system and, because the volume of the microspheres mustbe accommodated, requires the use of larger volumes of the adhesive andsealant to achieve the same bond or seal volume.

Consequently, it would be desirable to achieve encapsulated adhesive andsealant compositions in which the cell wall of the capsules is minimizedand the quantity of liquid curable component is increased.

It would also be desirable to achieve encapsulated adhesive and sealantcompositions having controlled flow characteristics, especially high orhigher viscosities than are traditionally found with encapsulatedadhesive and sealant compositions, and, in particular, having a fairlyconstant rheology over a larger temperature range, so as to enable theiruse in gap situations and other situations where squeeze-out or flow-outof the liquid curable material is undesirable.

It would also be desirable to achieve encapsulated adhesive and sealantcompositions wherein, even if premature rupturing or fracturing of thecapsules occurred, the composition was such that minimal, if any,reaction or polymerization of the curable or polymerizable componentswas able to occur.

It would also be desirable, especially for certain applications, toachieve the foregoing without the use of constituents or materials thatare not relevant to the bonding and/or sealing of the substrates andsurfaces to which they are to be applied.

It would also be desirable to achieve one-part storage stable adhesiveand sealant compositions which are especially suited for use in highspeed, industrial manufacturing processes.

It would also be desirable to achieve pre-applied adhesives which areable to withstand large pressures and forces without activation,especially in a pre-applied state on a given substrate.

SUMMARY OF THE INVENTION

According to the present invention there are provided microencapsulatedcure systems for initiating and/or effectuating, directly or indirectly,the cure or polymerization of adhesive and sealant compositions. Thesemicroencapsulated cure systems comprise at least one curing agent, acarrier in which the curing agent is dispersed as a discrete phase orwhere the curing agent is wholly or partly solubilized in or misciblewith the carrier, and a polymer shell encapsulating the carrier whereinthe carrier is, in the absence of external forces, a substantiallynon-flowing material. Preferably, the carrier is a material that is asolid or semi-solid at ambient temperature but softens or flows atelevated temperatures, a solid or semi-solid that softens or flows uponexposure to the liquid curable or polymerizable component of theadhesive or sealant, a putty-like or gel-like material, or a combinationof the latter that flows upon the application of modest force. Apreferred aspect of the encapsulated cure system is that the curingagent is substantially or totally prevented from allowing a substantialor total cure of the curable composition to which it is to be addeduntil an intimate mixing event occurs.

More specifically, the present invention is directed towards anencapsulated cure system for curable compositions comprising (a) acarrier material, (b) a curative contained in said carrier material, and(c) a polymer capsule encasing said carrier material wherein the carrieris a natural or synthetic material or composition that is substantiallynon-flowing in the absence of external forces or elevated temperatures.Preferably, the carrier material is (a) soft, putty-like or gel-like incharacter, (b) a solid or semi-solid that is (i) soluble in or issoftened by a liquid curable matrix component of the curable compositionwith which they are to be used, (ii) softened by the reaction and/orenvironmental conditions under which the curable composition is cured orpolymerized or (iii) is softened by the method or process by which thecurative is to be made available to the curable, polymerizable orcross-linkable component of said adhesive or sealant. In one embodiment,it is contemplated that the carrier, which may be of a soft putty-likeor gel-like character, comprises a thixotropic or thickened compositionof monomers, oligomers or pre-polymers, or a combination thereof, whichcomposition is substantially non-reactive with the curative in theencapsulated state. It is also contemplated that the carrier includes orcomprises one or more thixotropic agents or non-thixotropic gelling orthickening agents that are generated in-situ or act latently concurrentwith or following encapsulation of the carrier material. Among thevarious materials that may be considered for carrier there are given hotmelts, pressure sensitive adhesives, rubber materials,elastomer/tackifier compositions, polymers whose Tg is less than 35° C.,semi-solid and solid resins, starches and starch-based polymers,hydrogels, low temperature waxes and thickened or gelled masses of oneor more monomers, oligomers, prepolymers or mixtures thereof. In certainapplications, it is desirable that the carrier be an adhesive or havelatent adhesive properties. With those carriers where force is necessaryto flow or deform the carrier, such force must be of at least 1 psi. Itis also preferred that the curative dispersed or entrained in thecarrier be substantially non-migratory in said carrier and/or that thecapsule wall be substantially impermeable to the curative. For ease ofuse and more homogeneous distribution, it is especially desirable thatthe curative and carrier be miscible with one another. Generallyspeaking, the curative is present in an amount of from about 0.1 wt.percent to about 25 wt. percent based on the total weight of theencapsulated cure system and/or the shell comprises from about 0.8 wt.percent to about 25 wt. percent of the encapsulated cure system.

In an alternate embodiment, the encapsulated cure system of the presentinvention comprises (a) a carrier material, (b) a curative contained insaid carrier material, and (c) a polymer capsule encasing said carriermaterial wherein the carrier is a natural or synthetic material orcomposition that is substantially non-flowing in the absence of externalforces or elevated temperatures which carrier material is formedin-situ, concurrent with or subsequent to encapsulation, from a liquidcarrier precursor composition having dispersed or dissolved therein thecurative.

The present invention also pertains to the methods by which theforegoing encapsulated cure systems are prepared. Such methods includethe (1) encapsulation of a non-liquid carrier particle having containedtherein the curing agent, (2) the encapsulation of a dispersion of aheat and/or shear sensitive material in which the curing agent isdispersed or dissolved, said heat and/or shear sensitive material beingsolid or viscous at room temperature and/or in the absence of high shearforces but liquid or flowable at an elevated temperature and/or whensubjected to high shear forces, and (3) the encapsulation of adispersion of liquid beads of a liquid precursor composition in whichthe curing agent is dissolved or dispersed, which precursor compositioncures or polymerizes without consuming any of the curing agent or, ifthe curing agent is consumed, without consuming all or substantially allof the curing agent. In one aspect of the latter method, the cure of theprecursor composition occurs in-situ, concurrent with or subsequent tothe formation of the capsule wall. Said curing may be effected, in wholeor in part, by the curing agent to be encapsulated or, preferably, byanother curing agent suitable for effecting cure or polymerization ofthe polymerizable or curable components of the carrier precursorcomposition. Additionally, the second and third methods mentioned abovemay involve materials or precursor compositions that (a) are inherentlyor include components that are latent gelling and/or thickening agentsor (b) form such gelling or thickening agents in-situ. Such thickeningor gelling agents may be temperature dependent or time and sheardependent or react to form a gel in-situ.

More specifically, the present invention is directed to a method ofmaking an encapsulated cure system for effecting polymerization of acurable composition wherein the method comprising the steps of:

a) homogeneously dispersing or dissolving a curative in a monomer,oligomer and/or prepolymer composition for which said activator issubstantially inactive,

b) creating fine droplets of the composition of (a),

c) polymerizing said droplets and,

d) encapsulating the polymerized droplets in a breakable polymericmaterial.

Various methods may be employed for creating the aforementioned dropletsincluding precipitation polymerization, solution polymerization,suspension polymerization and dispersion polymerization.

In another embodiment the method may comprise the steps of:

a) homogeneously dispersing or dissolving a curative in a monomer,oligomer and/or prepolymer composition for which said activator issubstantially inactive,

b) creating fine droplets of (a),

c) encapsulating the fine droplets of (a) in a second polymerizablematerial and

d) polymerizing said second polymerizable material prior to orconcurrent with the polymerization of the encapsulated droplets. Hereencapsulation may be accomplished by coacervation, interfacialpolymerization, air suspension, centrifugal extrusion, spray drying, pancoating, or by adding the fine droplets of (a) to a dispersion of thesecond polymerizable material and applying a pressure shock wave to thedispersion.

In yet another embodiment, the method of making the encapsulated curesystem comprises the steps of:

a) homogeneously dispersing or dissolving a curative in a monomer,oligomer and/or prepolymer composition for which said activator issubstantially inactive,

b) polymerizing the composition of (a),

c) converting the polymerized composition of (a) to a particulate formand

d) encapsulating the particles in a breakable polymeric material.

Alternatively the method may comprise the steps of:

a) homogeneously dispersing a curative in a melt of a heat sensitivematerial which is non-reactive with the curative,

b) creating a dispersion, emulsion or suspension of the melt in a liquidmedium suitable therefore,

c) encapsulating the so formed beads of the melt in a breakablepolymeric material, and

d) lowering the temperature of the solution to harden the melt prior to,concurrent with or subsequent to the encapsulation step.

The present invention also pertains to curable and polymerizablecompositions comprising the above-mentioned encapsulated cure systems.Such curable and polymerizable compositions may be in the form ofone-part (one-package) liquid curable systems having the encapsulatedcure system dispersed in the liquid curable component. Alternatively,the curable and polymerizable compositions may be a dry blend ofencapsulated cure system particles and encapsulated curable componentparticles. Still further, such curable compositions according to thepresent invention may comprise a liquid binder containing a mixture ofencapsulated cure system particles and encapsulated curable and/orpolymerizable component particles. The present invention also pertainsto substrates having the last mentioned curable/polymerizablecompositions pre-applied thereto and methods of activating suchcurable/polymerizable compositions.

More specifically the present invention is also directed to curable andpolymerizable compositions comprising one or more curable orpolymerizable monomers, oligomers and/or prepolymers and one or moreencapsulated curatives, as described above, wherein at least one of theencapsulated curatives comprises (a) a carrier material, (b) a curativecontained in said carrier material, and (c) a polymer capsule encasingsaid carrier material wherein the carrier material is a natural orsynthetic material or composition that is substantially non-flowing inthe absence of external forces or elevated temperatures. Preferably, thecarrier material is (a) soft, putty-like or gel-like in character, (b) asolid or semi-solid that is (i) soluble in or is softened by a liquidcurable matrix component of the curable composition with which they areto be used, (ii) softened by the reaction and/or environmentalconditions under which the curable composition is cured or polymerizedor (iii) is softened by the method or process by which the curative isto be made available to the curable, polymerizable or cross-linkablecomponent of said adhesive or sealant. Such carrier materials mayinclude or comprise one or more thixotropic, non-thixotropic gelling ornon-thixotropic thickening agents, particularly those which may be slowacting or latent in nature, or the foregoing may be generated in-situ inthe carrier concurrent with or following encapsulation of the carriermaterial. Suitable curable or polymerizable monomers, oligomers and/orprepolymers include those that undergo vinyl polymerization, i.e., thosehaving at least one vinyl group CH2=CH— and/or reactive unsaturation(i.e., —C═C—); unsaturated polyesters; urethanes; epoxy resins;polysulfides; isocyanates; silicones; polyethers, polyurethanes andpolyolefins having silanol moieties capable of undergoing silanolcondensation or hydrosilation reactions; and phenoxy resins. In itspreferred embodiment, the curative dispersed or entrained in the carrieris substantially non-migratory in said carrier and/or that the capsulewall is substantially impermeable to the curative and/or thepolymerizable components.

In following, the present invention is also directed to suchpolymerizable compositions wherein only one of the curatives necessaryfor effectuating polymerization, cure or cross-linking of the curablecomposition is contained in the encapsulated carrier and any othercuratives that may be necessary are either dispersed or dissolved in thecurable components or are inherently present on the substrate surface towhich they are to be applied. In yet another alternative embodiment, thecurable composition comprises at least two different encapsulated curesystems each comprising a different carrier material and/or a differentcurative. An especially important feature of the present invention isthat no or substantially no polymerization, cure or cross-linking of thecurable components takes place, even if the capsule wall of theencapsulated cure system of the present invention is breached unless anduntil conditions are attained for releasing or exposing the entrainedcurative in the carrier to the curable components of the curablecomposition and, if necessary, the remaining curatives needed tocomplete or activate the cure system.

In yet another embodiment, the present invention relates to curablecompositions that may be pre-applied to a substrate, which may be in theform of an industrial or commercial stock material, article ofmanufacture, etc., wherein the curable components thereof are alsoencapsulated. In such embodiments, the various encapsulated componentsare dispersed in a suitable binder for applying or holding the same tothe substrate.

The present invention also relates to substrates, which may be in theform of an industrial or commercial stock material, article ofmanufacture, etc., that have applied thereto a pre-applied curablecomposition of the types mentioned above.

In yet another aspect, the present invention relates to industrialbonding processes wherein the encapsulate cure systems described aboveand the curable compositions comprising the same, also as mentionedabove, are employed.

DETAILED DESCRIPTION

Curing agents suitable for use in the practice of the present inventionvary widely. Selection of the specific curing agent depends upon thechemistry of the curable or polymerizable adhesive and/or sealantmaterial, the nature or cure mechanism of the adhesive or sealant to becured, the method and/or conditions by which the curing agent and/orpolymerization or cure of the adhesive or sealant is to be effectuated,the end-use application and/or the nature of the substrate to which theadhesive or sealant is to be applied, and the compatibility of thecuring agent with the carrier, its precursors and/or the encapsulatingmaterial. One class of curing agents includes those involved with thecross-linking of polymer and pre-polymer materials including curativesand hardeners as well as agents used in conjunction therewith forinitiating, accelerating, catalyzing, etc. the cross-linking orhardening of such materials. Another class of curing agents includethose involved with the polymerization of one or more polymerizablemonomers, prepolymers and/or low molecular weight polymers including,for example, activators, co-activators, accelerators, co-accelerators,catalysts, co-catalysts, initiators and co-initiators; especially thoseinvolved with free-radical polymerization. For convenience, unlessotherwise stated herein, the terms “curative(s)” and “curing agents”shall, when used herein and in the appended claims, mean all suchagents. Specific examples of the various curatives are disclosed in moredetail below in relation to the discussion on the various adhesive andsealant systems with which they are employed.

The polymerizable or curable or cross-linkable adhesive and sealantcompositions, of which the curative forms a part, suitable for use inthe practice of the present invention also vary widely. Selection of thespecific adhesive or sealant composition depends upon the end-useapplication to which it is applied and the environment that it willexperience, the cure mechanism to be employed, the process or method bywhich the curative is to be made available to the curable, polymerizableor cross-linkable component of said adhesive or sealant, as well as thecompatibility thereof with the carrier to be used. Generally speaking,the present invention is applicable to most one-part and two- or morepart adhesive and sealant compositions, as more fully disclosed in thisspecification. While encapsulation is not currently used for traditionalone-part, liquid systems, the present invention allows one to apply aone-part, liquid system to a substrate which, during processing of thesubstrate, is exposed to conditions that would or might otherwiseinitiate or cause polymerization or cure of the one-part system. Forexample, a heat curable one-part adhesive or sealant may be pre-appliedto a substrate which, during processing, but before cure orpolymerization is desired, is subjected to heat otherwise sufficient toinitiate cured or polymerization of the one-part system. Forconvenience, unless otherwise stated, the term “curable composition(s)”shall, when used herein and in the appended claims, mean all suchcurable, polymerizable and/or cross-linkable adhesive and sealantcompositions. In the same light, unless the context of the text or claimmakes clear that the specified term is being employed in its traditionalmeaning, the terms “cure”, “polymerize” and “cross-link” shall be usedinterchangeably in this specification and in the appended claims.

The carrier may be any of a number of different materials depending uponthe process and materials to be used for preparing the capsules, theapplications to which the cure systems are to be used, the chemistry ofthe curable compositions in which they are to be employed and theprocess or method by which the curative is to be made available to thecurable, polymerizable or cross-linkable component of said curablecomposition. Generally speaking the carrier will be selected fromnatural and synthetic materials or compositions that are (a) soft,putty-like or gel-like in character or (b) solid or semi-solid so longas the solid or semi-solid carrier material is (i) soluble in or issoftened by the liquid curable matrix component of the curablecomposition with which they are to be used, (ii) is softened by thereaction and/or environmental conditions under which the curablecomposition is cured or polymerized and/or (iii) is softened by themethod or process by which the curative is to be made available to thecurable, polymerizable or cross-linkable component of said adhesive orsealant. The carrier may be comprised of substantially polymeric oroligomeric components and/or monomeric components provided that thecarrier composition itself exhibits the aforementioned characteristics.Furthermore, it is understood that the curing system of the presentinvention may comprise a mixture of different encapsulated carriers,each containing the same or a different curing agent. It is alsocontemplated that the carrier may be or may generate in-situ athixotropic material or latent thixotropic material; however, because ofthe small particle size of the microcapsules, thixotropy must beinherent or made inherent to the composition or material comprising thecarrier. Traditional inorganic thixotropic additives such as fumedsilica and the like are, at this time, generally consideredinappropriate for use in the preparation of the microencapsulated curesystems of the present invention due to the relatively large particlesize of current day inorganic thixotropic additives as compared to theparticle size of the microencapsulated cure systems. Alternatively, orin addition, the carrier composition may include or comprise one or morenon-thixotropic gelling or thickening agents that act latently such thatthe carrier or carrier precursor material immediately prior to or duringthe encapsulation process is of a low viscosity and followingencapsulation is of an increased viscosity, generated in-situ. As usedin this application and the appended claims, the terms “soft” and“putty-like” mean that the referenced materials do not flow or deformwithout moderate force, generally without a force of at least 1 psi,preferably at least 5 psi. These soft or putty-like materials may haveno or little to moderate elasticity, preferably a consistency and degreeof elasticity of from that of cake frosting to that of bread dough, sothat as sufficient and repetitive forces are acted upon the encapsulatedcarrier, more of the curative within the carrier material is exposedand/or made available. Similarly, reference to softening of the carriermaterial means that the carrier material becomes soft or putty-like oreven flowable upon exposure to certain materials and/or conditionsincluding, for example, upon exposure to the liquid components of thecurable composition in which the carrier is wholly or partly soluble,miscible or swellable or to heat or by mastication in the case of arubbery carrier material.

Exemplary of the materials that may be suitable for use as a carrierinclude any of a number of low Tg materials including hot melts,pressure sensitive adhesives, rubber materials and other low Tgpolymers, semi-solid and solid resins, starches and starch-basedpolymers, hydrogels, and low temperature waxes provided that theforegoing meet one or more of the aforementioned characteristics and donot interfere with the cure or polymerization or cross-linking of thecurable compositions or materially degrade the desired adhesive orsealant properties of the so cured, polymerized or cross-linkedcompositions.

The carrier may also comprise or include organic and inorganicthixotropic, thickening and gelling agents, particularly those usedcommercially to control the flow and rheology characteristics of, forexample, paints, adhesives, sealants, engine and industrial oils, andfood products. Suitable organic polymeric thickening or gelling agentsinclude styrene/olefinic block copolymers sold under the Kraton brand,and a variety of small molecules that can associate chemically orphysically, such as various plasticizers, thickeners, flow controlagents, and the like. As noted previously, current conventionalinorganic thixotropic, thickening and gelling agents are typically notsuitable for use in the preparation of the microencapsulated cure systemunless the particle size of such inorganic additive is extremely smalland the particle size of bead of the carrier material or carrierprecursor material to be encapsulated is very large. However, shouldtechnology evolve whereby nano-sized inorganic thixotropic, thickeningand gelling agents are capable of being produced, it is certainlycontemplated that those materials will have applicability in thepractice of the present invention.

On the other hand, it is also contemplated that the carrier or thecomponents thereof may be co-reactive with the curable compositionand/or the curative. For example, with respect to the former, thecarrier may have a functional group that serves as a reactive orcross-link site with and during polymerization or cure of thepolymerizable monomers, pre-polymers and/or polymers of the curablecomposition. Alternatively, and preferably, the carrier composition maycomprise (a) a mixture (“mixture (a)”) of one or more liquid mono-and/or poly-functional monomers, oligomers and/or prepolymers thatcopolymerize with the liquid curable components of the curablecompositions and (b) a viscosity modifier which is (i) a slow acting,latent gelling or thickening agent, (ii) a temperature activated gellingor thickening agent (no gel at elevated temperatures) and/or (iii) ashear sensitive gelling or thickening agent. In this embodiment, thecarrier composition is subjected to conditions whereby the compositionis of low viscosity, i.e., where the viscosity modifier has no orsubstantially no effect, at that point during the encapsulation processwherein the fine beads or droplets of the mixture (a) are prepared forencapsulation and returns to or becomes of a much higher viscosity,exhibiting the characteristics of the carrier as defined earlier,subsequent thereto. For example, the elevated temperature or shearforces which lower the viscosity may be removed following formation ofthe droplets and prior to, concurrent with, or subsequent to theapplication or deposit of the shell wall or shell wall forming material.Alternatively, following formation of the droplets, the emulsion,dispersion, suspension, colloid, etc. of the mixture (a) may be subjectto such conditions as effectuate or accelerate the gelling or thickeningproperties of the latent gelling or thickening agent Employing carrierscomprised of the mixture (a) has the added benefit of maximizing theamount of liquid curable components in the final curable composition andminimizing the amount of other inert ingredients and/or ingredientswhich may affect the properties of the cured or polymerized curablecomposition.

It should be noted that where the carrier is a thickened or gelled orthixotropic material, the viscosity at the time of formation of thebeads is low such that low or moderate shear forces create finedroplets, consistent with the desired particle size and particle sizedistribution of the to be formed encapsulated cure system. In theirthickened, gelled or thixotropic state, the viscosity is such that evenmoderate to high shear forces will not allow for the preparation of afine, preferably substantially uniform, droplets or for droplets havinga very narrow and traditional bell curve particle size distribution.

As noted above, the curative may also take part in the polymerization ofcertain or all components of the carrier composition provided that theamount of curative incorporated into the carrier precursor compositionis sufficient so that adequate amounts remain following completion ofthe polymerization of the carrier so as to be able to effectuate cure ofthe curable composition. Preferably, though, the curing agent for thecurable composition is not, or is not to any meaningful extent, involvedwith the cure or polymerization of the carrier. Instead, the carrierprecursor composition includes one or more other curing agents, leavingthe encapsulated curing agent available for effecting cure orpolymerization of the curable composition. In any event, it is importantthat the curative to be incorporated into the carrier not react with thecarrier once formed so as to ensure long-term shelf stability andefficacy of the curative in the encapsulated carrier. Of course, thecurative may, and most likely is, involved with the chemical reactionbetween the carrier and the curable components of the curablecomposition, if any. The key is that the curative not be reactive withthe carrier in its encapsulated form.

Furthermore, the carrier may have incorporated therein other componentsof the adhesive or sealant or other additives pertinent to the carrieritself including, for example, plasticizers to enhance the pliability orsoftness of the carrier and/or tackifier resins. Again, however, it isimportant that such other components not interfere with the cure orpolymerization or cross-linking of the curable compositions ormaterially degrade the desired adhesive or sealant properties of the socured, polymerized or cross-linked compositions. Suitable plasticizersinclude phthalates, adipates, hydrocarbon resins, oils, and fatty acidesters, including, for example, methyl palmitate and methyl stearate.Especially preferred plasticizers are those based on polybutenes andcombinations thereof alone or together with other additives such asaliphatic lactate esters as taught in Wyffels (U.S. Pat. No. 5,688,850),incorporated herein by reference. Suitable tackifier resins includealiphatic and/or aromatic hydrocarbon resins and terpene resins.

While the carrier may be an inert material from the perspective ofbonding or sealing, it is preferred that the carrier itself participatein the bonding or sealing performance of the overall adhesive or sealantsystem in which it is incorporated. Specifically, it is oftentimesdesirable for the carrier to possess inherent or latent adhesive orsealant properties. For example, the carrier may be or contain a hotmelt adhesive, a pressure sensitive adhesive, an elastomer/tackifiercomposition, a thickened or gelled mass of one or more monomers,oligomers or mixtures thereof, etc. By employing a carrier which hasadhesive characteristics, the carrier is able to provide an initial andimmediate bond between two substrates to be bonded, holding the two inproper alignment while providing sufficient time for the curablecomposition to cure, polymerize or cross-link, as appropriate. This isparticularly beneficial in high speed, industrial bonding applicationswhere only a very brief time, on the order of fractions of a second, arepossible to apply pressure between the two substrates to be bonded. Thisattribute is of even greater significance in those instances where thesubstrates to be bonded have forces, whether inherent in the productdesign and/or materials of which they are made, etc., that, in theabsence of an immediate tack bond, would cause the two substrates tocome apart: thus, making a bond impossible. For example, in bondingopposing end flaps of a cereal box whose natural tendency is to open,the use of a carrier with adhesive characteristics will hold the flapstogether while the curable or polymerizable material cures orpolymerizes to form the formal bond.

It is also contemplated that the curing system of the present inventionmay comprise a mixture of two or more different microencapsulatedcarriers each containing the same or a different curing agent and/orcarrier material. For example, one may tailor the adhesivecharacteristics contributed by the carrier by employing a combination ofcarrier particles, some of which contain a higher percentage of materialwith latent adhesive properties and others with a carrier material oflow or no adhesive properties. Alternatively, a portion of the carrierparticles may comprise a gel containing a mixture of mono- and/or orpoly-functional monomers that are co-polymerizable with the curablecomposition and the remainder comprise an adhesive. Such compositionsprovide limited, quick bonding capability with more liquid curablecomponents so as to enhance the adhesive composition while lessening theamount of non-participating, non-reactive carrier. In essence, the useof mixtures of different carrier particles enables one to balance theimmediate and latent adhesive properties of the ultimate adhesivecomposition.

As noted, the carrier material may be a hydrogel. Suitable hydrogelsinclude, but are not limited to, those derived from gelatin,polysaccharides, alginates, cross-linked polyacrylamide polymers,hydroxyethylmethacrylate polymers, crosslinked polyhydroxyethylacrylate,polymerized, crosslinked 2-acrylamido-2-methylpropane sulfonic acidpolymers and their salts, including particularly the sodium andpotassium salts, crosslinked polyvinylpyrrolidone, polyacrylic acid,copolymers of the foregoing with each other and/or other polymers suchas polystyrene or other non-hydrogel forming polymers. An exemplaryhydrogel is that based on poly-2-hydroxyethylmethacrylate, preferablycross-linked with ethylene glycol dimethacrylate.

The carrier may also be an elastomer composition. Exemplary elastomersare those exhibiting a second order glass transition temperature (Tg),or a softening point, of less than 25° C., preferably less than about 0°C., especially those soluble in (meth)acrylate ester monomers. Suchelastomers are synthetic high polymers with exhibit plastic flow,particularly, polychloroprene and copolymers of butadiene or isoprenewith styrene, acrylonitrile, (meth)acrylate esters, and the like.Additional useful elastomers include copolymers of ethylene and(meth)acrylate esters, homopolymers of epichlorohydrin and copolymers ofepichlorohydrin and ethylene oxide. Specific examples includeCR-neoprene-polychloroprene, NBR-nitrile rubber-butadiene-acrylonitrilecopolymer, styrene-butadiene copolymer, acrylic rubber acrylatebutadiene copolymer, and copolymers of ethylene and acrylate esters suchas methylacrylate and ethylacrylate. Of course, higher Tg materials maybe used, especially where the curable composition is to be activated athigher temperatures or otherwise experiences higher temperatures duringactivation, e.g., where friction of mixing or the mixer element createshigher temperatures. Also included in this class of materials are theso-called rubber resin adhesives which comprise an elastomericingredient such as crude natural rubber, styrene-butadiene elastomer, apolybutadiene, polyisobutylene and polysiloxane and a tackifying resinsuch as glyceryl esters of hydrogenated rosin, thermoplastic terpeneresins, petroleum hydrocarbon resins, coumarone-indene resins, syntheticphenol resins, low-molecular weight polybutenes and tackifying siliconeresins.

The carrier may also be an adhesive or pressure sensitive adhesivematerial having a low Tg or low softening point, preferably less than25° C. and having an elastic modulus of less than about 5×10⁵ dynes/cm2at 70° C., as measured using a dynamic mechanical thermal analyzer ModelRSA II (available from Rheometrics Co.). Suitable adhesives include theacrylate-based pressure sensitive adhesives, particularly those thatgenerally do not require the addition of a tackifier resin. Suchacrylates typically have alkyl chains of from 1 to 14 carbon atoms permolecule, preferably from 4 to 12 carbon atoms per molecule. A mixtureof different acrylate monomers may be used, but at least a major portionof the alcohol residue forming the alkyl tails of the moleculesgenerally have carbon-to-carbon chains of at least four carbon atomsterminating at the ester linkages. Examples of useful acrylate-basedpolymeric materials are the homo- and co-polymers of methylisoamylacrylate, isooctyl acrylate, commercial fuse oil acrylate and2-ethylhexylacrylate. The copolymers may include acrylic acid,methacrylic acid, acrylamide, methacrylamide, acrylonitrile andmethacrylonitrile as co-monomers. Other acrylic materials includemulti-component compositions comprising, for example, a low Tg acrylatemonomer such as n-butyl acrylate, ethyl acrylate, 2-methylbutylacrylate, isobutyl acrylate, isooctyl acrylate, 2-ethyl hexyl acrylateand the like, a functional monomer such as N,N-dimethyl(meth)acrylamide,N,N-diethyl(meth)acrylamide, N-vinylpyrrolidone and the like, and ahigher Tg acrylate monomer such as 3,5-dimethyladamantyl (meth)acrylate,isobornyl (meth)acrylate, 4-bipheny (meth)acrylate, and 2-nephthyl(meth)acrylate. Still another class of pressure sensitive materials arethe acrylic hot melt PSAs of Mancinelli (U.S. Pat. No. 5,225,470),incorporated herein by reference.

The present invention is particularly suited for those carriermaterials, particularly pressure sensitive adhesive materials, that arepolymerized in-situ, i.e., concurrent with or subsequent to,encapsulation of the carrier. Exemplary systems include those disclosedin, for example Schwantes (U.S. Pat. No. 6,592,990) and Nagai et. al.Such systems generally comprise addition polymerizable pre-polymers,including, for example, alkyl (meth)acrylate, aralkyl (meth)acrylate,cycloalkyl (meth)acrylate, alkoxy (meth)acrylate, cycloalkoxy(meth)acrylate, bicycloalkyl (meth)acrylate, and alkoxy (alkoxy)_(n)(meth)acrylate. The alkyl moieties should be selected preferably of 1 to16 carbons, the cycloalkyl moieties from 4 to 8 carbons, and n is aninteger from 1 to 6.

More particularly suitable addition polymerizable pre-polymers includethose whose homopolymer has a Tg of less than about 0° C., a flash pointof at least 75° C., and a boiling point of at least 175° C., including,for example, n-pentyl acrylate, 2-methyl butyl acrylate, 2-ethylhexylacrylate, n-octyl acrylate, n-decyl acrylate, n-dodecyl acrylate, laurylmethacrylate, lauryl acrylate, 2-ethylhexyl methacrylate, n-octylmethacrylate, iso-octyl acrylate, isooctyl methacrylate, isononylacrylate, isodecyl acrylate, 2-ethoxyethyl methacrylate, butyl diglycolmethacrylate, tetrahydrofurfuryl acrylate, 2-phenoxyethyl acrylate,isohexyl acrylate, tridecyl acrylate, tridecyl methacrylate, ethoxylatednonyl phenol acrylate and the like and mixtures thereof.

Optionally, the in-situ formed carrier may contain a terpene resin inaddition to the polymerizable prepolymer. Terpene resins function astackifiers and, for purposes of the invention, include wood rosinresins, esters of gum rosin, styrenated terpene and terpene phenolicresins (including CAS #259094-71-8). Examples of terpene resins includemodified terpene resins, such as those sold under the Sylvares™ andZonatac™ tradenames (Arizona Chemical, Panama City, Fla.), as well asthe ester-modified or polyol ester modified terpene resins such asSylvalite™ (CAS#8050-26-8) and the like.

Optionally, the composition from which the in-situ formed carrier isderived may include a second substantially water insoluble polymerizablepre-polymer which pre-polymer is multifunctional having at least twoaddition polymerizable sites. By “substantially water insoluble” ismeant that the material has a solubility in water of less than about 2%,more preferably less than 1%, by weight. The addition polymerizablesites of said prepolymers interact with other addition polymerizablesites in the transformation of the pre-polymers to an encapsulated tackyadhesive material. Exemplary second substantially water insolublepolymerizable pre-polymers include allyl methacrylate, alkene glycoldimethacrylate, alkyl dimethacrylate, alkyldiol dimethacrylate, alkoxyalkanol diacrylate, trialkanol triacrylate, alkoxy(alkoxy)_(n) alkyltriacrylate, alkoxy (alkoxy)_(n) alkyl dimethacrylate, aralkyldimethacrylate, cycloalkyl dimethacrylate, alkoxy dimethacrylate,bicycloalkyl dimethacrylate, cycloalkoxy dimethacrylate, allyl acrylate,alkene glycol diacrylate, alkyl diacrylate, alkyldiol diacrylate, alkoxyalkanol dimethacrylate, trialkanol trimethacrylate, alkoxy (alkoxy)_(n)alkyl trimethacrylate, alkoxy (alkoxy)_(n) alkyl diacrylate, aralkyldiacrylate, cycloalkyl diacrylate, alkoxy diacrylate, bicycloalkyldiacrylate, cycloalkoxy diacrylate, wherein the alkyl moieties are of 1to 16 carbons, the cycloalkyl moieties are of 4 to 8 carbons, n is aninteger from 1 to 6. More specifically, the second substantially waterinsoluble polymerizable pre-polymer having at least two additionpolymerizable sites can be selected from any of allyl methacrylate;triethylene glycol dimethacrylate; ethylene glycol dimethacrylate;tetraethylene glycol dimethacrylate; polyethylene glycol dimethacrylate;1,3 butylene glycol diacrylate; 1,4-butanediol dimethacrylate;1,4-butanediol diacrylate; diethylene glycol diacrylate; diethyleneglycol dimethacrylate; 1,6 hexanediol diacrylate; 1,6 hexanedioldimethacrylate; neopentyl glycol diacrylate; neopentyl glycoldimethacrylate, polyethylene glycol diacrylate; tetraethylene glycoldiacrylate; triethylene glycol diacrylate; 1,3 butylene glycoldimethacrylate; tripropylene glycol diacrylate; ethoxylated bisphenoldiacrylate; ethoxylated bisphenol dimethacrylate; dipropylene glycoldiacrylate; alkoxylated hexanediol diacrylate; alkoxylated cyclohexanedimethanol diacrylate; propoxylated neopentyl glycol diacrylate,trimethylolpropane trimethacrylate; trimethylolpropane triacrylate,pentaerythritol triacrylate, ethoxylated trimethylolpropane triacrylate,propoxylated trimethylolpropane triacrylate, propoxylated glyceryltriacrylate, di-(trimethylolpropane) tetraacrylate, dipentaerythritolpentaacrylate, ethoxylated pentaerythritol tetraacrylate, and the like,and mixtures thereof.

The second substantially water insoluble polymerizable pre-polymer canhave at least three different mechanisms for forming a tacky adhesivewith the first pre-polymer. The second polymerizable pre-polymer canhave two reactive sites or polyfunctional sites for reacting with thefirst pre-polymer. Alternatively, the second pre-polymer can be selectedto have polar groups such as oxygen, amine, ether, ester, alcohol,ketone, hydroxy, epoxy, carboxylic acid, or aryl acid, withoutlimitation, for purposes of hydrogen bonding with other polar groups ofthe adhesive forming polymer. Yet a third alternative is to select thesecond pre-polymer such that it stericly entangles or hinders themovement of opposing chains of the adhesive being formed.

Suitable second substantially water insoluble polymerizable pre-polymershaving polar groups can be selected from the group consisting of alkoxy(meth)acrylates, polyester (meth)acrylate, alkoxy(alkoxy)_(n) alkyl(meth)acrylate, (meth)acrylalkoxy phthalic acid, glycidyl(meth)acrylate, cycloalkoxy (meth)acrylate, and acyloxy (meth)acrylatewherein said alkyl moieties are from one to sixteen carbons, wherein thecycloalkyl moieties are from four to eight carbons, wherein n is aninteger from one to six. Specific examples of the second substantiallywater insoluble polymerizable pre-polymer includes materials selectedfrom the group consisting of butyl diethyleneglycol methacrylate,2-methoxyethyl acrylate; 2-ethoxyethyl methacrylate; butyl diglycolmethacrylate; t-butylaminoethyl methacrylate;2-(2-oxoimidazolidin-1-yl-ethyl) methacrylate; tetrahydrofurfurylmethacrylate; tetrahydrofurfuryl acrylate; 2-phenoxyethyl acrylate;2-phenoxyethyl methacrylate; glycidyl methacrylate; ethoxylated nonylphenol acrylate; ethoxylated hydroxyethyl methacrylate; alkoxylatedtetrahydrofurfuryl acrylate; ethoxylated nonyl phenol methacrylate;alkoxylated nonyl phenol acrylate; caprolactone acrylate; 2-acryloxyethoxy-o-phthalic acid; 2-acryloxy-1-methylethoxy-o-phthalic acid and2-acryloxy-1-methylethoxy-o-dihydro-(3,6)-phthalic acid.

As stated above, another alternative for the second substantially waterinsoluble polymerizable pre-polymers are pre-polymers that result insteric entanglement or that stericly hinder the movement of opposingchains of the adhesive forming polymer. Such prepolymers include, forexample, alkyl (meth)acrylates of greater than 14 carbons, cycloalkyl(meth)acrylates, multicyclic alkyl (meth)acrylate, aralkyl(meth)acrylate, and cycloalkoxy (meth)acrylate, wherein the alkylmoieties are of at least 14 carbons, and wherein the cycloalkyl moietiesare of at least 6 carbons. Exemplary of the substantially waterinsoluble polymerizable pre-polymer which stericly hinders the firstwater insoluble polymerizable pre-polymer are stearyl acrylate; stearylmethacrylate; acrylate C 18-22, dicyclopentenyloxyethyl methacrylate;dicyclopentyl oxyethyl methacrylate; isobornyl methacrylate; isobornylacrylate; benzyl acrylate; benzyl methacrylate; cyclohexyl acrylate;cyclohexyl methacrylate; and cetyl acrylate. Some of the materialsidentified as participating in hydrogen bonding earlier, such astetrahydrofurfuryl methacrylate, tetrahydrofurfuryl acrylate, 2-phenoxyethyl acrylate and 2-phenoxy ethyl methacrylate can also function asstericly hindering pre-polymers.

For effecting in-situ polymerization of the carrier, the carrierprecursor composition typically includes a catalytically effectiveamount of a substantially water insoluble free radical initiator alongwith the addition polymerizable pre-polymer(s) and, if present, solvent.The solvent provides a medium in which the various prepolymer materialscan undergo polymerization. Suitable solvents include petroleum oils,vegetable oils, vegetable oil esters, liquid hydrocarbon resins, liquidplasticizers and blends thereof. The free radical initiator is selectedto have a half-life of at most 10 hours at 25° C., and more preferablyat most 1 hour at 25° C. The free radical initiator needs to be solublein the polymerizable pre-polymer material and solvent. The free radicalinitiator can be selected from the group of initiators comprising an azoinitiator, peroxide, dialkyl peroxide, alkyl peroxide, peroxyester,peroxycarbonate, peroxyketone and peroxydicarbonate. More particularlythe free radical initiator is selected from 2,2′-azobis(isobutylnitrile), 2,2′-azobis(2,4-dimethylpentanenitrile), 2,2′-azobis(2,4-dimethylvaleronitrile), 2,2′-azobis(2-methylpropanenitrile),2,2′-azobis (methylbutyronitrile), 1,1′-azobis(cyclohexanecarbonitrile),1,1′-azobis(cyanocyclohexane), benzoyl peroxide, decanoyl peroxide;lauroyl peroxide; benzoyl peroxide, di(n-propyl)peroxydicarbonate,di(sec-butyl)peroxydicarbonate, di(2-ethylhexyl)peroxydicarbonate,1,1-dimethyl-3-hydroxybutyl peroxyneodecanoate, α-cumylperoxyneoheptanoate, t-amyl peroxyneodecanoate, t-butylperoxyneodecanoate, t-amyl peroxypivalate, t-butyl peroxypivalate,2,5-dimethyl 2,5-di (2-ethylhexanoyl peroxy) hexane, t-amylperoxy-2-ethyl-hexanoate, t-butyl peroxy-2-ethylhexanoate, t-butylperoxyacetate, di-t-amyl peroxyacetate, t-butyl peroxide, di-t-amylperoxide, 2,5-dimethyl-2,5-di-(t-butylperoxy)hexyne-3, cumenehydroperoxide, 1,1-di-(t-butylperoxy)-3,3,5-trimethyl-cyclohexane,1,1-di-(t-butylperoxy)-cyclohexane, 1,1-di-(t-amylperoxy)-cyclohexane,ethyl-3,3-di-(t-butylperoxy)-butyrate, t-amyl perbenzoate, t-butylperbenzoate and ethyl 3,3-di-(t-amylperoxy)-butyrate.

In yet another alternative embodiment of the present invention, thecarrier material may be one that is heat sensitive, i.e., one thattransforms from a solid or semi-solid state to a liquid or putty-likestate upon exposure to relatively low temperatures. In particular, suchcarriers have a melting point or range above ambient temperature (˜25°C.) and are substantially insoluble in the encapsulating medium and,preferably, will have substantial, or at least partial, solubility inthe curable composition at temperatures above the melting point, or inand above the melting range. Preferably the disperse phase has a meltingpoint or range in the range 35° C.-150° C., more preferably in the range40° C.-85° C. Suitable heat sensitive carrier materials includepolyethylene glycols, preferably having molecular weights in the range4000 to 20,000; acid waxes; stearic acid and stearates. A particularlysuitable material is polyethylene glycol of average molecular weight4000, which is a wax. Other suitable materials are described in Cookeet. al. (U.S. Pat. Nos. 4,497,916 and 3,547,851), incorporated herein byreference.

Finally, other suitable carriers include, for example, the corematerials disclosed in Gosiewski et. al. (U.S. Pat. No. 5,206,288),Cahalan et. al. (U.S. Pat. No. 4,768,523), Sataki et. al. (U.S. Pat. No.5,814,685), Everaerts et. al. (U.S. Pat. Nos. 5,905,099 and 5,612,136),Mudge (U.S. Pat. No. 4,908,268), Sanderson et. al. (U.S. Pat. No.4,077,926), Mancinelli (U.S. Pat. Nos. 5,225,470 and 5,006,582), Iovineet. al. (U.S. Pat. No. 4,721,748), and Petras et. al. (U.S. Pat. No.4,061,826), all of which are herein incorporated by reference.

The cure system of the present invention also includes a polymer shellencasing the carrier particle. Suitable materials for forming thepolymer shell include any of those know in the art for encapsulation,particularly the encapsulation of liquid droplets or solid particles.Selection of the encapsulating material is dependent upon the desiredproperties of the shell wall, the chemical composition of the carrieror, in the case of a carrier to be cured or polymerized in-situ after orconcurrent with formation of the shell, the carrier precursor materials,including the curative, and the method employed for the encapsulationprocess. It is also important that the composition of the shell wall besuch that it is impermeable to the curative, particularly where thecarrier is of a composition that allows for the migration of thecurative within the carrier or the blooming of the curative from withinthe carrier.

The shell wall may be a rigid material or a flexible material so long asthe wall ruptures under the conditions for initiating polymerization,curing or cross-linking of the curable composition. For the purpose ofthis application, it is understood that reference herein to “initiation”or “initiating” polymerization, curing or cross-linking includes thatstep where the curative is brought into direct contact with or otherwisemade available to the polymerizable components of the curablecomposition, regardless of whether actual polymerization, curing orcross-linking is concurrently effected. For example, in activatedanaerobic curable compositions, the polymerization is initiated;however, polymerization does not occur in the presence of air due tooxygen inhibition. Similarly, a heat activated curative may beintimately mixed with the curable component of the curable composition,but polymerization does not occur until the proper temperature isattained to effectuate heat activation. In essence, but for the absenceof a physical or environmental condition or a chemical co-reactant whichis inherently supplied by the substrate upon which the adhesive isapplied or to be applied, polymerization or cure would commence.

The thickness of the shell wall may vary widely and may range from anextremely thin film that provides no or little structural effect butmerely serves as an impermeable or low permeability barrier for thecurative to a shell wall having structural integrity of its own. Suchthin walls are particularly suitable for those curing systems whereinthe carrier is a stiff or rigid material. Alternatively, thicker shellwalls may be employed, especially where the microcapsules during theformulation or application of the adhesive or sealant composition or thesubstrates to which it is applied are subject to extensive shearconditions, strong forces, excessive handling, etc. Thicker walls arealso appropriate where the carrier is very soft or thixotropic in natureand, by itself, provides little or less than desired resistance todeformation.

Permeability refers to the ability of the shell wall to provide adequateprotection against the ingress and/or egress of materials into or fromthe microcapsule that may otherwise affect the shelf life of themicrocapsules and/or the adhesive or sealant formulation into which theyare incorporated. Thus, the shell wall may be permeable to certainmaterials so long as it does not adversely affect the utility andefficacy of the microcapsules for their defined life, which life istypically three months, preferably six months or more.

Generally speaking, it is an objective of the present invention toemploy thin shell walls, especially shell walls thinner than aretraditionally used for or found with current microencapsulated one-partadhesive systems; though, of course, such thinner walls are not requiredand traditional thickness walls may also be used. However, the use ofthin shell walls is especially desirable as their use means that more ofthe components necessary for forming the adhesive or sealant and lessinert, filler material, as represented by the shell wall, are present ina given volume of adhesive or in the bond site. Typically, in accordancewith the practice of the present invention, the shell wall will comprisefrom about 0.8 wt. percent to about 25 wt. percent, preferably fromabout 2 wt. percent to about 12 wt. percent, most preferably from about4 wt. percent to about 10 wt. percent of the whole of the curing system.

The cure systems of the present invention are prepared in a two-stepprocess, the first being the incorporation of the curative in thecarrier and the second the encapsulation of the modified carrier. Aswill be readily apparent to those skilled in the art, any number of avariety of methods may be used for accomplishing both of these steps.However, the selection of the specific processes will depend upon anumber of factors including, in particular, the materials to be used andthe point at which the curative is to be incorporated into the carrier.

The curative may be incorporated into the carrier material in a numberof different ways depending upon the selection of curative and carriermaterials and the ability and manner by which such carrier materials areconverted into particle form. In one embodiment where the carrier is asolid or semi-solid material, the curative is compounded or kneaded intothe carrier material and, if the resultant material is sufficientlyrigid, ground to the desired particle size or if not rigid, frozen andthen ground to the desired particle size. For example, the curative maybe incorporated into a polymer melt of the carrier or, if the carrierwere a wax, the curative would be blended into the liquefied wax andthen the mix hardened. Yet again, the curative could be kneaded into asoft, pliable or malleable polymeric or elastomeric carrier using a rollmixer, Banbury mixer or the like. In essence any of the known methodsfor incorporating a solid or semi-solid into another solid or semi-solidmay be employed provided that the processing conditions are such as notto adversely affect or degrade the curative.

Where the curative is a liquid or in solution, it is possible to use asolid or semi-solid carrier that absorbs or is swelled by the liquidcurative or solvent of the curative solution. In this process, thecarrier acts much like a sponge, whereby liquid curative is absorbedinto the carrier or, if a solution, the solvent brings the curative intothe carrier. In those cases involving a curative solution, the solventis preferably allowed to evaporate prior to encapsulating, or if thecarrier following such evaporation is not in the proper particulateform, grinding the carrier prior to encapsulation. However, it is notalways necessary to drive off the solvent or all of the solvent wherethe solvent of the curative solution acts as a plasticizer for thecarrier, thus, softening the carrier to facilitate access to or exposureof the curative upon initiation, without interfering with or having adetrimental impact on the performance or desired properties of the curedadhesive or sealant.

Alternatively, where the carrier itself is in solution, the curative maybe added thereto before driving off the solvent and recovering themodified carrier. Alternatively, depending upon the carrier and thenature of the carrier solution, certain additives, pH adjustments and/ortemperature changes and the like can be employed to precipitate out themodified carrier,

Another approach to the incorporation of the curative into the carrieris by dispersing or dissolving, whether wholly or partly soluble ormiscible, the curative in one or more of the precursor materials orreactants that are used to form the carrier material. If the curative isalso effective in initiating, accelerating or facilitating the cure orpolymerization of the carrier, then sufficient excess of the curativemust be used to ensure that adequate curing agent remains in the carrierfollowing its formation. This reaction mix may then be cured orpolymerized to form the modified carrier and the so formed mass groundto the desired particle size. Alternatively, the aforementioned reactionmix or the components thereof may be added to an appropriate liquidmedium and subjected to shear mixing so as to form a colloidal solution,suspension or emulsion. The colloidal solution, suspension or emulsionmay then be subject to the appropriate conditions for effecting cure orpolymerization of the reaction mix to form the modified carrierparticles prior to encapsulation or an appropriate encapsulatingmaterial may be added to the solution for effecting encapsulation of thereaction mix droplets and thereafter forming the capsule or shell wall,with or without concurrent in-situ polymerization or cure of the carriermaterial. Any of the known methods for encapsulating a liquid may beemployed including techniques based on interfacial polymerization,coacervation, and the like.

The amount of curative to be incorporated into the carrier depends uponthe specific curative or curatives to be employed and the curablecomposition with which it is be used, the method by which initiation ofcure of the curable composition is to be accomplished, the anticipatedweight ratio of curable composition to encapsulated cure system and, asnoted above, whether the curative also participates in or is consumed bythe cure or polymerization of the carrier material and/or shell wall.Generally speaking, the amount of curative will be consistent with thoselevels typically used to effectuate cure of the given curablecomposition. However, where the process by which the carrier and curablecomposition are mixed involves intimate mixing, e.g., repetitivekneading or mastication, it is often possible to employ lower levels ofthe curative for the same volume of curable composition due to the moreefficient exposure of the curative to the curable components.

When the encapsulated curative is to be employed in additionpolymerizable curable compositions, the curative will be present in anamount of from about 0.1 wt. percent to about 25 wt. percent, preferablyfrom about 1 wt. percent to about 20 wt. percent, most preferably fromabout 5 wt. percent to about 15 wt. percent of the carrier. Higheramounts are also contemplated; however, with such higher amount, less ofthe encapsulated carrier will be incorporated into the curablecomposition for a given particle size. Furthermore, since the density ofthe carrier particles in a curable composition is lessened as theconcentration of the curative in the carrier particles increases and/oras the particle size of the carrier particles increase (in order tomaintain a given amount of curative for a given volume of curablecomponents), it may be necessary to employ more intimate mixing orkneading of the carrier particles during the activation step to ensure athorough dispersion/distribution of the curative in the curablecomposition.

Where the curative is a cross-linking or hardening agent, typicallyemployed with step growth polymerization reactions, the amount of suchcuratives in the microcapsules will be considerably higher. Suchcuratives will typically be present in an amount of from about 2 wt.percent to about 50 wt. percent, preferably from about 10 wt. percent toabout 30 wt. percent, most preferably from about 15 wt. percent to about25 wt. percent of the carrier. More importantly, the amount of thesecuratives typically is dependent upon the stoichiometry requirements forthe curable composition and the degree of cross-linking, as appropriate,that may be desired. Thus, higher or lower amounts may be used in thecarrier particles with proper adjustment of the amount of carrierparticles to be incorporated into a given amount of curable composition.

Generally speaking, the encapsulated carrier microparticles of thepresent invention serve as microdomains of the curing agent in a highlyconcentrated amount. Where the curative also serves as the curative forthe carrier and/or the microcapsule walls, the curative is typicallyincorporated at a level that is at least 2 times, preferable at least 5times and most preferably at least 10 times that necessary foreffectuating cure of the carrier and/or wall material. In this instance,the amounts recited in the prior two paragraphs refer to the amount ofcurative following polymerization and/or cure of the carrier and/or cellwall, as appropriate.

The particle size of the encapsulated cure system of the presentinvention may vary widely depending upon the intended end-useapplication, the method by which the cure of the curable compositionwith which they are to be used is initiated and the constraints of themethod by which the particles are formed. Typically, the volume weightedmedian particle size will range from about 2 microns to about 200microns, preferably from about 5 microns to about 50 microns, mostpreferably from about 10 microns to about 20 microns. Volume weightedmedian particle size is determined using an Accusizer 788, made byParticle Sizing Systems of Santa Barbara, Calif.

As noted above, microencapsulation of the carrier material may beattained through any of the known methods and using any of the knownmaterials. While the following discussion is predominately directedtowards the encapsulation of the carrier, the same is equally applicableto the encapsulation of other components of the curable compositions,where desired or applicable, including, specifically, the liquid curablecomponents as discussed further below. Suitable techniques includecoacervation, interfacial polymerization, air suspension, centrifugalextrusion, spray drying, pan coating, in-situ polymerization, and byforming a dispersion of core material and shell material and applying apressure shock wave to the dispersion as described in Redding Jr. (U.S.Pat. No. 5,271,881, incorporated herein by reference). The specificselection of the method and the materials depends upon the nature,including the physical state and/or chemistry, of the material to beencapsulated, e.g., whether the carrier material is in a liquid form ora solid, semi-solid or gel-like particulate form. Exemplary methods andmaterials are set forth in the following paragraphs as well as in, forexample, Schwantes (U.S. Pat. No. 6,592,990), Nagai et. al. (U.S. Pat.No. 4,708,924), Baker et. al. (U.S. Pat. No. 4,166,152), Wojciak (U.S.Pat. No. 4,093,556), Matsukawa et. al. (U.S. Pat. No. 3,965,033),Matsukawa (U.S. Pat. No. 3,660,304), Ozono (U.S. Pat. No. 4,588,639),Irgarashi et. al. (U.S. Pat. No. 4,610,927), Brown et. al. (U.S. Pat.No. 4,552,811), Scher (U.S. Pat. No. 4,285,720), Shioi et. al. (U.S.Pat. No. 4,601,863), Kiritani et. al. (U.S. Pat. No. 3,886,085), Jahnset. al. (U.S. Pat. Nos. 5,596,051 and 5,292,835), Matson (U.S. Pat. No.3,516,941), Chao (U.S. Pat. No. 6,375,872), Foris et. al. (U.S. Pat.Nos. 4,001,140; 4,087,376; 4,089,802 and 4,100,103), Greene et. al.(U.S. Pat. Nos. 2,800,458 and 2,730,456), Clark (U.S. Pat. No.6,531,156), Saeki et. al. (U.S. Pat. Nos. 4,251,386 and 4,356,109),Hoshi et. al. (U.S. Pat. No. 4,221,710), Hayford (U.S. Pat. No.4,444,699), Hasler et. al. (U.S. Pat. No. 5,105,823), Stevens (U.S. Pat.No. 4,197,346), Riecke (U.S. Pat. No. 4,622,267), Greiner et. al. (U.S.Pat. No. 4,547,429), and Tice et. al. (U.S. Pat. No. 5,407,609), amongothers and as taught by Herbig in the chapter entitled “Encapsulation”in Kirk Othmer, Encyclopedia of Chemical Technology, V. 13, SecondEdition, pages 436-456 and by Huber et. al. in “Capsular Adhesives”,TAPPI, Vol. 49, No. 5, pages 41A-44A, May 1966, all of which areincorporated herein by reference.

The first step in the encapsulation process is the preparation of thediscrete particles, domains or beads of the carrier material or carrierprecursor materials. Where such materials are in solution or liquid formand the encapsulation is to be by way of, e.g., coacervation,interfacial polymerization, etc., the solution or liquid containing thecarrier or carrier precursor material is subjected to high shear mixingor agitation to create a suspension, emulsion or colloidal system ofdiscrete domains of the carrier or carrier precursor of the requisitesize. Where the carrier is a heat sensitive material, e.g., a wax orwax-like material, the carrier, with the therein incorporated curative,is heated above its melt temperature and then subjected to a similarhigh shear mixing or agitation in a liquid medium, preferably water, tocreate discrete droplets of the carrier and then cooled to allow thesolid particles to form, before encapsulating. Where the curative isincorporated into a solid or substantially solid carrier, the carriermay be ground and sorted to the desired particle size beforeencapsulation. Such methods, as well as additional alternative methodsfor preparation of the particles or discrete domains for encapsulationare widely used in industry and well known to those skilled in the art.

One preferred microencapsulation technique is coacervation wherein thematerial to be encapsulated is dispersed or emulsified in a liquidsolution of the material to be used as the wall material. The solutionis perturbed to cause a phase separation of the wall material, or atleast a portion thereof, from the solvent with all or some of the wallmaterial coating the dispersed material to be encapsulated. In thisprocess, the wall forming material may directly separate out onto theemulsified or dispersed core material or it may form its own emulsionwith the droplets of the wall material subsequently depositing on thedroplets of the core material. In either case, the liquid wall materialdeposits itself as a continuous coating about the dispersed droplets ofthe internal phase or capsule core material and the wall material isthen solidified. Solution perturbation can be any that affects thesolubility of the wall material including changes in temperature andaddition of another solvent, including, for example, the addition of anon-solvent for the wall material. It should be readily understood bythose skilled in the art that the foregoing may be accompanied by a pHshift with wall materials such as gelatin to promote the phaseseparation in the wall formation step, as taught in Green (U.S. Pat.Nos. 2,800,457 and 2,800,458, incorporated herein by reference).

In coacervation encapsulation, the material to be coated is typically aliquid and is emulsified in the solvent to form droplets which are thencoated with the wall material. Oftentimes it is advantageous to alsoemploy an emulsification agent to assist with the emulsification of thecarrier materials or precursors thereof. Preferred emulsification agentsthat can be used are amphiphilic, that is, they contain both hydrophilicand hydrophobic groups in the same molecule. Exemplary emulsificationagents include, but are not limited to, partially hydrolyzed polyvinylalcohol, starch derivatives, cellulose derivatives, polyacrylamide, andthe like. A preferred emulsification agent for use in the invention ispartially hydrolyzed polyvinyl alcohol. In a preferred method, highshear agitation is provided to the aqueous mixture to achieve a dropletsize of less than about 250 microns, preferably less than 100 microns.

The conditions for encapsulation will vary based upon the choice of thematerials or compositions used for the capsule wall as well as thematerial to be encapsulated. Selection of the encapsulating materials orcompositions depends upon a number of additional factors including thedesired properties of the shell wall to be formed, the chemicalcomposition and state of the material to be encapsulated and, in thecase of a carrier material to be cured or polymerized in-situ concurrentwith or subsequent to formation of the shell wall, the carrier precursormaterials, including the curative and the method employed for theencapsulation process. Desired properties of the shell wall includestrength, breakability, and impermeability, at least with respect to thecurative in the case of the encapsulated cure system, particularly wherethe carrier is of a composition that allows for the migration orblooming of the curative in the carrier. Suitable materials for thecapsule walls include natural materials such as gelatin, gum arabic,starches, sugars, shellac, and rosin, cellulose derivatives, such asethyl cellulose and carboxymethylcellulose, paraffin, tristearin,polymers such as polyvinyl alcohol, polyethylene, polypropylene,polystyrene, polyacrylamides, polyethers, polyesters, polyamides,polybutadiene, polyisoprene, silicones, epoxies, polyurethanes,formaldehyde resins such as reaction products of formaldehyde withphenols, urea, and melamine, and copolymers such as polyurethanecopolyethers. Melamine-formaldehyde and polyvinyl alcohol are preferredwall materials, especially the former.

Dyes, pigments, fillers, plasticizers, crosslinking agents, bindingagents, and other additives can be incorporated in the capsule wall orapplied to the capsule wall surface. One important parameter to keep inmind when formulating wall materials is permeability. Generally, thewall material should have low permeability, at least with respect to thematerial to be encapsulated. No or low permeability of the capsule wallis particularly important with respect to the curative in the carrier soas to prevent loss of the curative and premature polymerization of thecurable composition. Likewise, it may be important for the capsule wallto be impermeable or of low permeability to the curable component of thecurable composition so as to prevent any ingress of the same into thecarrier particles. Dependent upon the encapsulated material, it may alsobe desirable to formulate the wall material to have low permeability tocertain gases such as oxygen or low permeability to liquids such aswater or solvents such as toluene or tetrahydrofuran. The requisitepermeation rates will vary for each system, but can be met by judiciouschoice of the wall material and by degree of crosslinking of the wallmaterial. Generally, as crosslinking increases, the permeation ratedecreases.

As noted above, any of a number of different processes may be used toencapsulate the carrier materials as well as other components of thecurable compositions. One preferred technique is to polymerize thecapsule wall material in-situ. In this technique, monomers or oligomersare dispersed on the material to be encapsulated and then polymerizationis effected by addition of a reactive species, such as a co-monomer orradical initiator, a curing agent or by heat or ultraviolet radiation.Optionally, the capsule wall material may be crosslinked in-situ byaddition of crosslinking agents or by treatment with heat or ultravioletradiation or radical initiators. The method of polymerizing orcrosslinking the capsule wall material will vary based upon the choiceof wall materials and based upon the material being encapsulated.

When the walls of the microcapsules are comprised of polyamide orpolyurea, a preferred encapsulation technique is interfacialpolymerization. This can be effected by mixing the adhesive monomer ormonomers to be microencapsulated together with either an acid chlorideor an isocyanate. The resultant mixture is emulsified with anemulsification agent to obtain an oil-in-water emulsion. Apolyfunctional amino compound is then added into the emulsion, wherebymicrocapsule walls are formed around each microparticle of oil. When anacid chloride is mixed with the polyfunctional amino compound, apolyamide microcapsule is produced—when an isocyanate is used, polyureacapsules are formed. Though reference is made to microparticles of theoil phase, it is also understood that the dispersed phase is alsoreferred to herein as “domain”, “bead” or “droplet” and the like.

Acid chlorides that can be used in the invention to produce polyamidemicrocapsules include, but are not limited to: terephthaloyl chloride,isophthaloyl chloride, 1,3,5-benzenetricarboxylic acid chloride, sebacyldichloride, 4,4-sulfonyidibenzoyl chloride, 1,3-benzenedisulfonylchloride, 1,4-benzenedisulfonyl chloride, or mixtures thereof. Apreferred acid chloride for use in the invention is a mixture ofisophthaloyl chloride and terephthaloyl chloride.

Isocyanate compounds that can be used in the invention to producepolyurea microcapsules include, but are not limited to: 2,4- and2,6-diisocyanatotoluene, 4,4′-diisocyanatodiphenyl methane,1,3,5-trimethylbenzene-2,4-diisocyanate, 1,6-diisocyanatohexane,polymethylene polyphenyl isocyanate, polyisocyanates which additionallycontain biuret-, allophanate-, and carbodiimide groups, and the like.

Examples of polyfunctional amines that can be used in the inventioninclude, but are not limited to: ethylene diamine, diethylene triamine,triethylene tetramine, tetraethylene pentamine 1,6 hexanediamine,polyethyleneimine, bis-hexamethylenetriamine, and the like.

Matson (U.S. Pat. No. 3,516,941) teaches polymerization reactions inwhich the material to be encapsulated, or core material, is dissolved inan organic, hydrophobic oil phase which is dispersed in an aqueousphase. The aqueous phase has dissolved aminoplast resin formingmaterials which upon polymerization form the wall of the microcapsule. Adispersion of fine oil droplets is prepared using high shear agitation.Addition of an acid catalyst initiates the polycondensation forming theaminoplast resin within the aqueous phase, resulting in the formation ofan aminoplast polymer which is insoluble in both phases. As thepolymerization advances, the aminoplast polymer separates from theaqueous phase and deposits on the surface of the dispersed droplets ofthe oil phase to form a capsule wall at the interface of the two phases,thus encapsulating the core material. Polymerizations that involveamines and aldehydes are known as aminoplast encapsulations.Urea-formaldehyde, urea-resorcinol-formaldehyde,urea-melamine-formaldehyde, and melamine-formaldehyde, capsuleformations proceed in a like manner. In interfacial polymerization, thematerials to form the capsule wall are in separate phases, one in anaqueous phase and the other in an oil phase. Polymerization occurs atthe phase boundary. Thus, a polymeric capsule shell wall forms at theinterface of the two phases thereby encapsulating the core material.Interfacial polymerization is particularly useful for wall materialssuch as polyesters, polyamides, and polyureas.

Gelatin and gelatin containing microcapsule wall materials are wellknown and are typically used in coacervation and phase separationencapsulation processes. One preferred technique for gelatin/gum arabicencapsulation involves first emulsifying the core material into agelatin solution to obtain an oil-in-water emulsion. The emulsion ismixed with a gum arabic solution. The system is then pH adjusted ordiluted to cause the gelatin/gum arabic to coacervate. Thereafter, thecapsules are post-treated with a crosslinking agent, such asformaldehyde, glutaraldehyde, or other similar known compounds.

Wall materials made of melamine-formaldehyde can be made by firstemulsifying the core material into a carboxyl methyl cellulose solutionor a poly(styrene-maleic anhydride) solution to obtain an oil-in-wateremulsion. The emulsion is then mixed with a melamine-formaldehydeprecondensate solution. The system is then pH adjusted, followed byheating to initiate polymerization of the precondensate to a highmolecular weight compound. The presence of the carboxyl methyl celluloseor poly(styrene-maleic anhydride) solution helps the polymerizedmelamine-formaldehyde to deposit onto the core material surfaces,thereby encapsulating the core. An alternative method polymerizes themelamine and formaldehyde in the presence of a styrene sulfonic acid.Yet, another alternative and a preferred embodiment of themelamine-formaldehyde resin wall forming process employs polyacrylicacid and/or polyacrylic acid derivatives and the like as emulsifiers toassist in forming the oil in water emulsions. Such emulsifierspreferably have an HLB value of from about 8 to 18.

Optionally, the wall material can be formed by free-radicalpolymerization or free radical crosslinking. This is especially usefulfor wall materials such as polvinyl chloride, polystyrene, acrylicesters (e.g. alkyl acrylate-acrylic acid copolymers), unsaturatedpolyesters and the like. The free radical reaction can be initiated byheat, ultraviolet radiation or by addition of initiators such as benzoylperoxide, t-amyl peroxyneodecanoate, t-amyl peroxypivalate, t-amylperoxy-2-ethyl-hexanoate, t-butyl peroxyisobutyrate, t-amyl perbenzoate,di-t-butyl peroxide, 2,2′-azobis(2-ethylbutyronitrile),2,2′-azobis(2,4-dimethylvaleronitrile),2,2′-azobis(2-methylpropanenitrile), and the like.

When the walls of the microcapsules are comprised of epoxies, suitablecomponents include difunctional or polyfunctional epoxides such asvinylcyclohexene dioxide,3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate,bis-phenol-A-digylcidyl ether and the like. These can be used incombination with polyols such as glycerol. One convenient method offorming microcapsules involves forming an emulsion of the material to beencapsulated, adding a combination of the di- or polyfunctional epoxidewith the polyol to coat the material to be encapsulated and then addingan acid to effect the polymerization and form the polyepoxide. Suitableacids include Bronsted acids such as hydrochloric acid or sulfuric acidand also Lewis acids such as boron trifluoride, antimony pentafluorideand the like.

The encapsulated cure systems of the present invention provide a numberof benefits and advantages to encapsulated adhesive and sealant systemswhich are neither found nor possible with the current conventionalencapsulated systems. In particular, as noted previously, the carriermay comprise a material that has inherent or latent adhesive propertiesor characteristics that, in use, provides a dual mode of bonding orsealing. Even if the carrier does not, by itself, provide any particularaction, it oftentimes will act as a structural filler providing addedstrength or durability to the adhesive or sealant material itself: thus,enhancing the cohesive strength of the adhesive or sealant. This isparticularly true where the carrier and the curable composition, eitherby their inherent nature or as a result of the process by which thecurable compositions are initiated and/or the curative is made availableto the polymerizable component of the adhesive or sealant, form aninterpenetrating network or otherwise become interspersed or aremiscible with each other. In essence, the curable composition may end upfilling voids, channels or pockets in and through the carrier.

While the foregoing are certainly beneficial and desirable attributes, amore important function of the carrier is to serve as a protectivereservoir for the curative and as a spatial protector for otherencapsulated components of the curable composition in or with which theyare used. First, because the curative is incorporated into the carrier,and is preferably not mobile within the carrier, the curative, or atleast a sufficient amount of the curative, is not generally available tothe polymerizable component, even in the absence of the encapsulatingshell. Instead, conditions must be imposed that convert the carrier to aflowable state and/or, in accordance with the preferred embodiment, thecarrier must be mechanically worked through a repetitive mashing orkneading type action to expose more and more of the entrapped curativeto the carrier surface and the liquid curable component. Thus, asdiscussed below, and except as noted below, conventional fingerpressure, pinch roll activation and the like found with traditionalencapsulated adhesive and sealant systems will not be sufficientgenerally to expose enough of the curative to provide adequate cure orpolymerization. While this then requires more action and, perhaps, morecostly or sophisticated equipment for initiating the cure, it means thatsuch adhesives and sealants can now be used in high stress environmentsand processes and/or applications where significant forces are actedupon the encapsulated adhesive prior to the desired or intended point ortime of initiation or activation. It also means that there is lessconcern or sensitivity for the method or process by which thesemicrocapsules are formulated into an adhesive or sealant composition andor the process by which they or the so formulated adhesive and sealantcompositions are dispensed or applied. Consequently, the presentinvention enables and facilitates the use of these types ofencapsulated, especially pre-applied encapsulated, adhesive and sealantcompositions in high speed industrial applications, especially thoseapplications where the adhesive or the pre-applied adhesive, asappropriate, is subject to intentional or unintentional forces that arecapable of pre-maturely rupturing the microcapsule walls.

In addition to protecting or preventing the release of the curative inthe event of premature rupture of the shell wall of the curativemicrocapsule, the curing systems of the present invention also act asspacers and protectors of other encapsulated components of curablesystems where one or more of the liquid components thereof are alsoencapsulated or preapplied and overlaid with an encapsulating film.Indeed, the carrier provides structural integrity to the microcapsule sothat, in use, the microcapsule acts much like the microspheres of theprior art, preventing the premature collapse or fracture of themicrocapsules containing the curable composition or other liquidcomponents. This attribute is especially beneficial where the curablecomposition, or at least the encapsulated cure system according to thepresent invention, is pre-applied to a substrate which is subsequentlystacked or in storage or handling comes in contact with othersubstrates, thereby applying pressure to the microcapsules containingthe carrier and curative. The structural integrity or resistance todeformation of the carrier material, in addition to the structuralintegrity of the capsule wall covering the carrier material, protectsthe microcapsules containing the liquid polymerizable or curablecomponents of the curable composition; provided, of course that thelatter are of about the same or smaller particle size. Slightly largerparticle sizes for the encapsulated curable composition are allowed solong as there is sufficient flexibility in their capsule walls to acceptthe initial pressure without rupturing before the encapsulated curesystem particles thereafter assume the primary burden of the pressure orforces acting upon the preapplied adhesive. Even if there were somerupturing of the capsules containing the liquid polymerizable or curablecomponents of the curable composition and/or the carrier, because thecurative is entrained within the carrier, as mentioned above, there isinsufficient curative available to initiate any significant cure orpolymerization.

The benefit of this spatial protection is not just limited to thepre-applied adhesives but also pertains to the formulated adhesive aswell as the encapsulated cure systems themselves, especially withrespect to their storage and handling stability. Because of thestructural integrity of the microcapsules resulting from the shell walland, more importantly, the carrier material, the microcapsules are lessprone to premature fracture or rupture. Furthermore, as noted above, thecells walls may have little structural integrity or strength themselves;rather, depending upon the carrier material, the structural integrity ofthe encapsulated cure system microcapsules may well be attributed to theencapsulated carrier itself. In such circumstance, there is littleconcern relative to the premature fracturing or rupturing of the cellwall since the curative within the carrier is still not available. Thus,less concern is needed for the packaging, handling and volume ofcontainers of the encapsulated cure system as well as curablecompositions into which they have been incorporated. In the former, theencapsulated cure systems will support one another. In the latter, theencapsulated cure system will support and bear the load of the othercapsules in the formulated composition, thus relieving the forces thatwould otherwise be acting upon the liquid capsules. Furthermore, even ifpremature fracture or rupture occurs, the curative contained within thecarrier is not lost and such carrier particles may be merelyre-encapsulated, if necessary.

Yet another key benefit of the encapsulated cure systems of the presentinvention is that when they are intimately mixed with liquidpolymerizable components of the curable composition, besides making thecurative available, the carrier itself is intimately mixed with theliquid curable components and provides a thickening and/or thixotropiceffect on the liquid curable components. This thickening effect lessensthe ease of or potential for squeeze out during the mating process oftwo substrates between which the curable composition is to be applied.More importantly, it allows for the use of liquid curable compositionson porous substrates as well as substrates having rough or unevensurfaces or where gaps are present when the two substrates to be bondedare mated. Specifically, this thickening effect on the liquid curablecomponents ensures or helps to ensure that the activated curablecomposition is more likely to stay where it is applied. Also, it allowsthe curable composition to be applied as a bead or raised ridge ofmaterial, again to ensure filling and/or bridging of any gap that mayexist. Although conventional liquid adhesives may be applied as a bead,their low viscosity does not allow the height of the bead to remain.Instead, the liquid bead will have a tendency to spread out forming moreof a flat tape-like bead of the liquid. While the beads of the presentinvention may not remain of their original height, the tendency to flowwill be less allowing more time to mate the substrates to be bonded. Inessence, like a scoop of ice cream, even the thickened adhesive beadwill have a tendency to slowly shorten and spread out.

In the present invention, the high viscosity or thickened bead may beformed after the intimate mixing of the components or concurrenttherewith. For example, as mentioned later, the activator mechanism orapparatus used to mix the components may be or include a series of damsor barriers that pushes and kneads the curable composition back andforth as the substrate upon which it is applied is passed through orpast the activator mechanism or apparatus. This apparatus acts like asnow plow leaving a bead or “bank” of the intimately mixed curablecomposition on the substrate as it emerges from the last dam or barrier.Alternatively, if a handheld or automated dispenser is employed thatincorporates a mixing means in the dispenser, the dispenser may be suchthat it includes an orifice from which a continuous or discontinuousbead of the intimately mixed curable composition is dispensed. Inessence, because of the thickening or gelling effect of the carrierparticle, the activated curable composition maybe applied to a substratein any number of profiles and is capable of maintaining, orsubstantially maintaining that profile for a prolonged period.

As noted above, the encapsulated cure systems of the present inventionmay be employed with a number of curable compositions: the selection ofthe curative in the encapsulated cure system being appropriate for thecure or polymerization mechanism to be used for effecting cure,polymerization and/or cross-linking of the polymerizable or curablecomponent of the curable composition. In this respect, it is to beunderstood that the curative(s) in any one microencapsulated carrier maynot represent the full complement of curatives or curing agents neededto complete the curing or polymerization or cross-linking of any givencurable composition. Thus, Applicants' reference to themicroencapsulated cure systems is to be understood as encompassingencapsulated carrier particles which incorporate the full complement ofcuratives needed as well as one or more, but not all, curatives neededfor effectuating the cure, polymerization and/or cross-linking of thecurable components of the curable compositions. Furthermore, it may beparticularly important, if not critical, in such circumstances that oneor more curatives or curing agents be isolated from one or more otherrequired curatives or curing agents.

Consequently, it is contemplated that curable compositions made inaccordance with the practice of the present invention may have dispersedor dissolved therein one or more of the required curatives provided thatthe same is not co-reactive therewith in the absence of the encapsulatedcurative contained in the carrier. Alternatively, or in additionthereto, particularly where one or more of the curable components of thecurable composition is also encapsulated, it is contemplated that one ormore of the curatives may be dispersed or dissolved therein andencapsulated therewith, again provided that the same is not co-reactivewith the encapsulated curable components in the absence of theencapsulated curative contained in the carrier. Yet another alternativeapproach incorporates a plurality of microencapsulated cure systems madein accordance with the teaching of the present invention, eachcontaining a different curative in a carrier. A preferred requirement ofthese possible embodiments is that all of the curatives needed toeffectuate the cure, polymerization and/or cross-linking of the curablecomposition are present in the formulated curable composition such thatwhen all of the curatives are made available to each other and to thecurable components of the curable composition and, if appropriate, theproper environmental conditions are met, e.g., elevated temperature orabsence of oxygen, then curing, polymerization and/or cross-linking willoccur. However, it is also understood that certain curatives criticalfor effecting polymerization, cure or cross-linking may inherently bepresent on the substrate surface to which the composition of the presentinvention is to be applied e.g., metal salts or oxides, in the case ofmetal substrates, or such curatives may be pre-applied to the substrateas a primer material, e.g., a solution of a curative in a solventcarrier may be used to prime or apply the curative to the substrate.

Generally speaking, the encapsulated cure systems of the presentinvention may be employed with essentially any curable or polymerizablechemistry, particularly any adhesive or sealant chemistry, regardless ofwhether the same is a one-, two- or more part system; a liquid system ordry-to the touch pre-applied system, especially those wherein the liquidcurable or polymerizable matrix monomers, prepolymers and/or polymersare encapsulated as well; and the like For any given application, themore critical factor is whether such application is amenable to or canit be adapted to allow for the processing or working of the adhesivecomposition needed for ensure adequate rupturing the shell of theencapsulated cure system and making available of the entrained curativein the carrier. While peeling away the shell will expose some of thecurative that is present on the outer surface of the carrier, the amountof curative thus available is not, or is not likely to be, sufficient toeffectuate adequate, if, indeed, any significant level of, cure,polymerization and/or cross-linking of the curable composition withwhich it is employed. Instead, the carrier must typically be subjectedto mixing, kneading or some other condition that maximizes the releaseor exposure of the therein-contained curative to the remainder of thecurable composition or at least to those constituents thereof that areneeded for effecting cure or polymerization.

As mentioned, the encapsulated cure systems of the present invention aresuitable for use in a broad variety of one-part liquid curable systems.With conventional encapsulated systems, concerns arise relative topremature fracture and/or polymerization of the curable composition dueto high shear forces during the preparation and/or dispensing of theliquid curable composition. However, with the encapsulated cure systemsof the present invention, the novel carrier systems alleviate concernsrelative to premature fracture and/or polymerization. Indeed, high shearforces during the preparation of the adhesive formulation and/or thedispensing of the same are typically insufficient to make availablesufficient curative to initiate premature polymerization or cure. On theother hand, for these new adhesive systems to be truly efficacious, itis desirable, and may be necessary, that the application and/or assemblyprocess in which the liquid curable system is employed provide for anappropriate opportunity or means for rendering the curative in thecarrier available for effecting or initiating polymerization of thecurable compositions. For example, the curable compositions of thepresent invention are suitable for use in bonding or sealing threadedelements where such threaded elements are subject to multiple turnsduring the assembly process. Threaded assemblies employing few or lessthan a whole turn as well as press/snap fit assemblies may realize somebonding provided a large shear is present; however, such assemblies orapplications are not encouraged. Similar limitations may be found wherethe capsule wall is ruptured and the curative made available, by pinchrolling or the application of finger pressure. In essence, such minimalaction on the carrier is oftentimes insufficient to release or makeavailable a suitable amount of curative necessary for effecting full oreven substantial cure or polymerization of the curable composition.Among the exceptions to this limitation, however, would be thoseencapsulated curative systems where the carrier is a wax and the liquidcurable composition containing the encapsulated cure system is exposedto sufficient heat to melt the wax prior to or concurrent with theapplication of pressure and/or mating of the two substrates to be joinedor where the carrier is a thixotropic material.

The more typical and, perhaps, practical use of the encapsulated curesystems of the present invention is in or in association withpre-applied adhesives, including any of the general types mentionedabove. It is in these compositions that the benefits of the moredifficult accessibility of or to the curative and the protective natureor spacer benefit of the encapsulated cure systems of the presentinvention come through. As above, however, it is critical that theapplication or assembly process in which the encapsulated cure system isemployed provides for the appropriate means for rendering the curativein the carrier available for effecting or initiating polymerization ofthe curable compositions.

Unlike the liquid curable compositions mentioned above which are appliedand cured at the time of intended use, pre-applied adhesives andsealants are applied in the manufacturing or conversion process of thesubstrate to which they are applied but not cured until later,oftentimes much later, depending upon the storage and shelf stability ofthe curable composition and demand for the stock material or substrateto which it is applied. Typically, the stock material or substrates towhich such adhesives or sealants are applied are stacked on top of oneanother or placed in containers where they come in contact with oneanother and/or are subjected to use or assembly operations where thereis the opportunity for many different forces and other substrates tocome in contact with the pre-applied material. Should the capsule orshell wall of the encapsulated cure system fail or rupture as a resultof such forces or activities, there is insufficient shearing and mixingof the carrier to make available adequate curative for effectingpremature polymerization, cure or cross-linking of the curablecomposition. Furthermore, in those pre-applied adhesive systemscomprising the encapsulated cure system dispersed in a liquidpolymerizable component, all of which is sandwiched between theunderlying substrate to which it is applied and an overlaying curedpolymer film or layer, when the depth of the layer of the liquidadhesive is less than the particle size of the encapsulated cure systemthe encapsulated cure system acts as a spacer to prevent the collapseand/or fracture of the polymer film. Similarly, in the more commonpre-applied encapsulated adhesive systems wherein the liquid curablecomponent is also encapsulated, when the average particle size of theencapsulated liquid components is less than, the same as or slightlylarger than the average particle size of the encapsulated cure system,the encapsulated cure system again acts as a spacer to prevent thecollapse and/or fracture of microcapsules containing the liquid curablecomponent. This latter aspect is especially beneficial since it allowsfor the use of capsules or shells that thinner than are traditionallyused in encapsulating the liquid curable component. This in turnprovides for a greater volume of liquid curable component thantraditionally found with the same volume of traditional encapsulatedadhesive and sealant compositions and, further, better bonding and/orsealing performance since more liquid is available at the interfacewhere the bond or seal is to be formed.

Another benefit of the encapsulated cure systems of the presentinvention is that they allow the user to tailor the curative to aspecific end use as well as regulate the cure speed even with the samecure system. For example, where the carrier is wholly or partiallysoluble in, miscible with or swellable by the liquid component of thecurable composition, the degree of solubility or swellability willaffect access to the curative in the carrier. Similarly, the ease withwhich the carrier is smeared or kneaded will also dictate the speed withthe curative is made available to the curable liquid. With a givenencapsulated cure system, the speed and duration for which the adhesiveor sealant system containing the curative is mixed will also affect thedegree and speed with which the curative and curable liquid is broughtinto intimate contact. For a given level of curative in the carrier, afaster and/or longer mixing will enhance the exposure of curative to thecurable liquid: thus speeding cure and/or facilitating a fuller cure ordegree of polymerization. Slower or less mixing will result in lessinteraction and slower and/or less overall cure.

As noted previously, the encapsulated cure systems of the presentinvention are useful for initiating and/or effectuating, directly orindirectly, the cure or polymerization of adhesive and sealantcompositions generally. Such cure or polymerization may be by way ofaddition polymerization, step growth polymerization or both. Additionpolymerization includes free radical polymerization, cationicpolymerization and anionic polymerization. Especially preferred freeradically polymerizable systems are those characterized as anaerobicadhesives and sealants, i.e., those that polymerize or cure in theabsence of air.

Generally speaking, suitable curable compositions include any of thoseheretofore known or hereafter found to be suitable or adaptable for thepreparation of one-part (i.e., single package) encapsulated adhesive andsealant compositions. Such compositions are characterized as beingstorage stable, curable compositions having one or more componentsisolated, through encapsulation, from other components, which curablecompositions, in the absence of such encapsulation, would polymerize orcure. Such curable compositions comprise the curative, which, accordingto the present invention, is contained in the carrier, and the liquid orviscous component or components of the adhesive or sealant compositions.In the practice of the present invention, the latter will notsubstantially change their physical state or phase, but rather remain ina liquid or viscous state, unless and until intermixed with thecurative, and, if applicable, exposed to the appropriate conditions foreffecting polymerization.

The liquid or viscous component of the curable composition may itself beencapsulated as with single package, dry adhesive and sealant systemswhich typically comprise a dry blend of microencapsulated components orwith liquid adhesive or sealant systems wherein the encapsulatedcomponents are dispersed in a liquid binder system or pre-applied to asubstrate by a cured or hardened binder system. Alternatively, thecurable composition may be a single package, wet adhesive or sealantsystem where the encapsulated carrier is dispersed in the liquid orviscous curable material. Though reference has most often been made toliquid curable components or the liquid adhesive or sealantcompositions, it is understood that such reference also includesflowable and/or non-flowing viscous materials and compositions as well.Similarly, while no substantive changes occur in the physical state orphase of the liquid curable component until the liquid or viscouscomponent is exposed to the curative, as noted below, such liquid orviscous compositions may further include or themselves comprisecompounds which increase in viscosity so long as the curable compositionremains in a liquid or viscous state or phase. Generally, the liquid orviscous polymerizable or curable components are in the form of lowmolecular weight monomers, oligomers and/or prepolymers.

Among the various classes of curable compositions suitable for usewithin the practice of the present invention are, for example, thosethat undergo vinyl polymerization, i.e., those having at least one vinylgroup CH2=CH— and/or reactive unsaturation (i.e., —C═C—); unsaturatedpolyesters; urethanes; epoxy resins; polysulfides; isocyanates;silicones; polyethers, polyurethanes and polyolefins having silanolmoieties capable of undergoing silanol condensation or hydrosilationreactions; and phenoxy resins. The present invention is also applicableto combinations of curable compositions within the same or differentclasses, regardless of whether they cure by the same or a differentmechanism. With the latter, the curative for each curable compositionmay be in the same or a different encapsulated carrier component.Alternatively, especially where the cure mechanism for one of thecurable compositions is a longer term, secondary type cure mechanism,the curative for that curable composition may be encapsulated with thecurable component for the other curable composition. Additionally, thecurable compositions of the present invention may be capable of bi-modalcure or polymerization, i.e., they are able to cure or polymerizethrough two different cure mechanisms. The latter may be especiallyfound with curable compositions that form linear polymer chains by onemechanism and cross-link by another. Furthermore, such compositions mayinclude a copolymerizable component and/or a secondary polymerizablecomponent which co-polymerizes or co-reacts with the primary componentor with secondary reactive sites on the primary polymer, respectively.

The curable compositions are based on low molecular weight, reactivemonomers, oligomers and/or pre-polymers which can be cured orpolymerized. Pre-polymer formulations typically include additionalco-polymerizable monomers and/or oligomers and are essentially apre-adhesive and/or pre-sealant. While the present invention iscertainly, and in certain applications preferably, applicable to stepgrowth polymerizable compositions, the requirement for properstoichiometry of the primary polymerizable component and the hardener orco-reactive component makes these curable compositions more difficult touse. Furthermore, depending upon the molecular size of the hardener orco-reactive component, such compositions may require a much largerweight percent of the carrier particles than addition polymerizablecompositions where the curatives tend to be low or lower molecularweight materials. Thus, the present invention is especially applicableto addition polymerizable compositions.

Preferred addition polymerizable curable compositions are those thatundergo vinyl addition, including those based on styrene and substitutedstyrenes such as alpha-methyl styrene; acrylamides; nitriles such ascyanoacrylates and methacrylonitriles; vinyl ketones such as ethyl vinylketone; vinyl esters such as vinyl acetate and vinyl proprionate;olefins such as ethylene, propylene and isobutylene; halogenated olefinssuch as vinyl chloride and vinylidene chloride; and diene monomers suchas butadiene, isoprene and chloroprene as well as copolymers of theforegoing such as vinyl chloride-vinyl acetate copolymer. Oftentimes itis desirable that such components be used in their oligomeric form,wherein the oligomer has residual unsaturation or another reactivemoiety or functional group, for example, hydroxyl, amino, carboxylic,epoxy and the like groups, which enables further polymerization orcross-linking.

For instance, an amine functionalized polystyrene oligomer may beemployed whereby initial cure or polymerization occurs at the point ofunsaturation concurrent with or followed by cross-linking at the aminefunctionality with, for example, an isocyanate.

Especially preferred additional polymerizable components are the poly-and mono-functional acrylate and methacrylate esters, i.e., monomers,oligomers and prepolymers having one or more acryloyl (i.e.,CH₂═C(R)COO—) and/or methacryloyl (i.e., CH₂═C(CH₃)COO—) terminal orpendent moieties. For convenience, as used herein and in the appendedclaims, reference to the term “(meth)acrylate” is to be understood asreferring to both the acrylate and the methacrylate versions of thespecified monomer, oligomer and/or prepolymer, (for example “allyl(meth)acrylate” indicates that both allyl methacrylate and allylacrylate are possible). Such materials encompass a broad spectrum ofpolymerizable components including, for example, polyesterpoly(meth)acrylates, urethane and polyurethane poly(meth)acrylates(especially those prepared by the reaction of an hydroxyalkyl(meth)acrylate with a polyisocyanate or a urethane polyisocyanate),methylcyanoacrylate, ethylcyanoacrylate, diethyleneglycoldi(meth)acrylate, trimethylolpropane tri(meth)acrylate, ethylene glycoldi(meth)acrylate, allyl (meth)acrylate, glycidyl (meth)acrylate,(meth)acrylate functional silicones, di-, tri- and tetraethylene glycoldi(meth)acrylate, dipropylene glycol di(meth)acrylate, polyethyleneglycol di(meth)acrylate, di(pentamethylene glycol) di(meth)acrylate,ethylene di(meth)acrylate, neopentyl glycol di(meth)acrylate,trimethylol propane tri(meth)acrylate, ethoxylated bisphenol Adi(meth)acrylates, bisphenol A di(meth)acrylates, diglyceroldi(meth)acrylate, tetraethylene glycol dichloroacrylate, 1,3-butanedioldi(meth)acrylate, neopentyl di(meth)acrylate, trimethylolpropanetri(meth)acrylate, polyethylene glycol di(meth)acrylate and dipropyleneglycol di(meth)acrylate. While di- and polyacrylates and methacrylates,especially the dimethacrylates, are the generally preferred materials.Monofunctional acrylates, i.e., those containing only one acrylategroup, may also be advantageously used. Typical monoacrylates include2-ethylhexyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, cyanoethyl(meth)acrylate, 2-hydroxypropyl (meth)acrylate, p-dimethylaminoethyl(meth)acrylate, lauryl (meth)acrylate, cyclohexyl (meth)acrylate,tetrahydrofurfuryl (meth)acrylate, chlorobenzyl (meth)acrylate, andglycidyl (meth)acrylate. Of course mixtures of (meth)acrylates or theirderivatives as well as combinations of one or more (meth)acrylatemonomers, oligomers and/or prepolymers or their derivatives with othercopolymerizable monomers, including acrylonitriles andmethacrylonitriles may be used as well.

(Meth)acrylates are typically polymerized by a free radical reaction.Initiators of free radical polymerization useful in the practice of thepresent invention include, but are not limited to peroxides,hydroperoxides, peresters, peracids, peroxycarbonates, peroxyketones,azo compounds and redox initiators, and derivatives of the foregoing.Exemplary initiators include benzoyl peroxide, cumene hydroperoxide,t-butyl hydroperoxide, dicumyl peroxide, decanoyl peroxide, lauroylperoxide, di-(n-propyl)peroxide, t-butyl peroxide acetate, t-butylperbenzoate, t-butylperoxybenzoate, t-butylperoxyacetate, di-t-butylazodiisobutyronitrile, t-amyl peroxyneodecanoate, dichlorobenzoylperoxide, methylethylketone hydroperoxide, t-butyl peroxide, t-amylperoxypivalate, t-amyl peroxy-2-ethyl-hexanoate, t-butylperoxyisobutyrate, di-sec-butyl peroxydicarbonate,di-(2-ethylhexyl)peroxydicarbonate, 1,1-dimethyl-3-hydroxybutylperoxyneodecanoate, α-cumyl peroxyneoheptanoate, t-amylperoxyneodecanoate, t-amyl peroxypivalate, t-butyl peroxypivalate,t-amyl peroxy-2-ethylhexanoate, t-amyl peroxyacetate, t-amylperbenzoate, di-t-butyl peroxide, 2,2′-azobis(2-methylbutyronitrile),2,2′-azobis(isobutyronitrile), 2,2′-azobis(2,4-dimethylpentanenitrile),2,2′-azobis(2,4-dimethylvaleronitrile),2,2′-azobis(2-methylpropanenitrile),1,1′-azobis(cyclohexanecarbonitrile), 1,1′-azobis (cyanocyclohexane) andthe like. Especially preferred initiators are the peroxides,hydroperoxides, peresters and peracids, most preferably benzoylperoxide. Typically such initiators are present at a level of from about0.01% to about 10%, preferably from about 0.5% to about 3.0%, mostpreferably from about 0.1% to about 2%, by weight based on the weight ofthe component(s) curable by the free radical polymerization.

In addition to the initiator, such free radical polymerizablecompositions further include an accelerator of free radicalpolymerization. Commonly known accelerators include amines andsulfimides. Tertiary amines, such as N,N-dimethylparatoluidine,triethylenetetramine, diethylenetriamine, N,N-dimethylaniline,N,N-diethylparatoluidine, and N,N-diethylaniline, and sulfimides such as3-oxo-2,3-dihydrobenz-[d]isothiazole-1,1-dioxide (saccharin) areparticularly useful. Useful accelerators also include the aldehyde-aminereaction products such as butyraldehyde-aniline andbutyraldehyde-butylamine. The most preferred accelerators, however, arethe organometallic compounds known as metallocenes, especially theferrocenes, and the organometallic polymers containing at least onemetallocene, preferably ferrocene, moiety. Exemplary organometallicaccelerators include ferrocene, butyl ferrocene, titanocene andcupricene. Accelerators are typically used at levels of from about 0.01%to about 1.0% by weight based on the weight of the component(s) curableby free radical polymerization. Notwithstanding the foregoing, thoseskilled in the art will recognize that the use of tertiary amines is ormay be preferred over the metallocenes in certain systems and/orapplications, especially those wherein there may be concern formigration of the metallocene into the curable binder system, especiallyUV curable binder systems, as mentioned below.

A preferred class of (meth)acrylate based curable compositions suitablefor use in the practice of the present invention are those know asanaerobic adhesive and sealant compositions. These compositionstypically comprise a free radically polymerizable monomer, oligomerand/or pre-polymer, a free radical initiator and a free radicalaccelerator, with or without a stabilizer or inhibitor such aspolyhydric phenols, quinones, and the like. Especially preferredpolymerizable monomers, oligomers and prepolymers include 2-hydroxyethyl(meth)acrylate, 2-hydroxypropyl (meth)acrylate, mono-, di-, tri- andtetra-ethylene glycol di(meth)acrylate, trimethylol propanetri(meth)acrylate, ethoxylated bisphenol A di(meth)acrylates, polyester(meth)acrylates and their derivatives, polyethylene glycol(meth)acrylates and their derivatives and polyurethane (meth)acrylatesand their derivatives. Suitable quinones include hydroquinones,benzoquinones, naphthaquinones, phenanthraquinones, anthraquinones andsubstituted compounds of the foregoing. These inhibitors preferably arepresent in the adhesive composition in only very small amounts, usuallyfrom about 10 to 1000 parts per million (ppm), and more preferably fromabout 50 to 500 ppm. The anaerobic compositions may also includechelators such as beta-diketones, ethylenediamine tetraacetic acid andthe sodium salt thereof. Anaerobic compositions are especially suitedfor applications where concern exists for premature curing orpolymerization of the curable components prior to mating of thesubstrates to be bonded or cured.

The present invention is also applicable to a broad array of epoxyresins including, but certainly not limited to, those of the typesdisclosed in Deckert et. al. (U.S. Pat. No. 3,746,068); Hart et. al.(U.S. Pat. No. 4,536,524); Earls et. al. (U.S. Pat. No. 5,510,431); andSiebert et. al. (U.S. Pat. Nos. 5,157,077 and 5,140,068), allincorporated herein by reference. Generally speaking, suitable epoxyresins typically comprise a mixture of low molecular weight oligomerscontaining, on average, two or more epoxide groups per molecule: thoughthey may also comprise oligomeric prepolymers of the foregoing. The mostcommon epoxy resins are those based upon glycidyl compounds, especiallythe glycidyl ethers such as those based on bisphenol A or on resorcinoland, to a lesser extent, the diglycidyl esters, especially thediglycidyl esters of phthalic acid, hexahydrophthalic acid andtetrahydrophthalic acid. Other suitable epoxy resins include thenovolak-epoxy resins, particularly those based on the phenol novolaks orcresol novolaks, the glycidyl ethers of glycerol, polypropylene glycolor pentaerythritol, as well as the glycidyl esters, glycidyl amines,epoxidized diene polymers and the cycloaliphatic epoxy resins.

The epoxy resins may be polymerized by treatment with hardeners orcuring agents that react with the epoxide group. Suitable curing agentsinclude aliphatic primary and secondary amines such asdiethylenetriamine, triethylenetetramine, and diethylaminopropylene;aromatic amines such as m-phenylenediamine, 4,4″-diaminodiphenylmethaneand diaminodiphenylsuphone; anhydrides, especially acid anhydrides, suchas phthalic, tetrahydrophthalic, hexahydrophthalic, maleic,pyromellitic, trimellitic, nadic methyl, dodecenylsuccinic andchlorendic anhydrides; and fatty polyamides. Other suitable curingagents include dicyandiamide, melamine, and imidazole derivatives;modified amines such as ethylene oxide- and acrylonitrile-epoxy resinadducts and ketimines, Lewis acids such as borontrifluoride-monoethylamine complex and Lewis bases such aso-(diethylaminoethyl)phenol, tris-(dimethylaminomethyl)phenol and2-ethyl-4-methyl imidiazole. For chemically curing or polymerizing theepoxy compounds and resins, a number of cationic initiators may be usedincluding HCl, HBr, HI, C₆H₅SO₃H, HSbF₆, HAsF₆, HBF₄ or Lewis acids suchas metal halide salts. The amount of curing agent added depends upon thespecific curing agent employed, but is typically 0.85 to 1.0 moles perepoxy stoichiometry, especially in the case of anhydrides or instoichiometric amounts in the case of amines, or from about 0.01% toabout 10%, preferably from about 0.1% to about 3% by weight, based onthe weight of the curable epoxy, in the case of cationic initiators forchemical curing. With the anhydrides, about 1% of a tertiary amine isalso employed as a catalyst. Those skilled in the art will readilyappreciate the proper selection and quantity of hardeners and catalyststo employ.

Oftentimes, and preferably depending upon the application, an epoxyprepolymer is reacted with a polyol and most preferably a polyester orpolyether polyol. Polyether polyols include linear and/or branchedpolyethers having a plurality of ether bonds and at least two hydroxylgroups. Examples of the polyether polyol include polyoxyalkylene polyolsuch as polyethylene ether glycol, polypropylene ether glycol,polybutylene ether glycol and the like. Suitable polyols includehomopolymers and copolymers thereof, especially copolymers of thepolyoxyalkylene polyols. Particularly preferable copolymers of thepolyoxyalkylene polyols may include an adduct with at least one compoundselected from the group consisting of ethylene glycol, propylene glycol,diethylene glycol, dipropylene glycol, triethylene glycol,2-ethylhexanediol-1,3,glycerin, 1,2,6-hexane triol, trimethylol propane,trimethylol ethane, tris(hydroxyphenyl)propane, triethanolamine,triisopropanolamine, ethylenediamine, and ethanolamine, with at leastone compound selected from the group consisting of ethylene oxide,propylene oxide and butylene oxide.

Polyester polyols are formed from the condensation of one or morepolyhydric alcohols having from 2 to 15 carbon atoms with one or morepolycarboxylic acids having from 2 to 14 carbon atoms. Examples ofsuitable polyhydric alcohols include ethylene glycol, propylene glycolsuch as 1,2-propylene glycol and 1,3-propylene glycol, glycerol,pentaerythritol, trimethylolpropane, 1,4,6-octanetriol, butanediol,pentanediol, hexanediol, dodecanediol, octanediol, glycerol monoallylether, glycerol monoethyl ether, diethylene glycol,1,3-bis-(2-hydroxyethoxy)-propane and the like. Examples ofpolycarboxylic acids include phthalic acid, isophthalic acid,terephthalic acid, maleic acid, octadecenylmaleic acid, fumaric acid,trimellitic acid, adipic acid, malonic acid, glutaric acid, and thecorresponding acid anhydrides, acid chlorides and acid esters such asphthalic anhydride, phthaloyl chloride, and the dimethyl ester ofphthalic acid. Preferred polycarboxylic acids are the aliphatic andcycloaliphatic dicarboxylic acids containing no more than 14 carbonatoms and the aromatic dicarboxylic acids containing no more than 14atoms.

The curable compositions may also be based on unsaturated polyesters,many of which are derived from the same monomers as the aforementionedpolyester polyols. Such unsaturated polyesters oftentimes exist ascombinations thereof with an unsaturated monomer as a diluent, such asstyrene. The unsaturated polyester resins are usually the product of areaction between one or more unsaturated dibasic acids and one or moredihydric alcohols, including those noted in the prior paragraph. Curingor polymerizing the unsaturated polyesters typically requires aninitiator and an accelerator; however, once free-radical polymerizationis initiated, such polymerization is self-sustaining. Suitableaccelerators include materials such as diethylaniline, dimethylanilineand N,N-dimethyl toluidine. Suitable initiators include such materialsas benzoyl peroxide, ethylmethyl ketone peroxide, cumene hydroperoxideand dichlorobenzoyl peroxide. Of course other accelerators andinitiators for the unsaturated polyesters may be used as well and arewell known to those skilled in the art.

Another class of curable polymeric resins to which the present inventionis applicable is the class of polyurethane prepolymer resins. Suchpolyurethane prepolymer resins include free isocyanate moieties orgroups as the reactive and polymerizing moiety of the molecule and aretypically the reaction product of poly(alkylene) glycols andpolyisocyanates. Specific polyurethane prepolymers include, for example,the reaction product of poly (1,4-butylene oxide) glycol and tolylenediisocyanate and/or methylene diisocyanate. Such resins may have as muchas 5 percent, by weight, of free isocyanate groups available forreaction. Curing agents suitable for use with the polyurethaneprepolymer resins include methylene-bis-(o-chloroaniline), polyols (suchas 1,4-butanediol), or trimethylolpropane, or even water. Other suitablepolyurethane resins include those that have free hydroxyl or olefinicfunctionality and cure through free radical polymerization. Suitablecatalysts for the polyurethanes include, among others, tin carboxylates,organosilicone titinates, alkyl titinates, bis carboxylates, tertiaryamines, amidines, tin mercaptides, and naphthenates or alkanoate saltsof lead, cobalt, manganese, bismuth or iron. Specific catalysts includetin(II) diacetate, tin(II) dioctanoate, tin(II) dilaurate, dibutyltindiacetate, dibutyltin dilaurate, dibutyltin maleate, stannous octoate,stannous oleate, stannous acetate, stannous laureate,2,3-dimethyl-3,4,5,6-tetrahydropyrimidine, triethylamine, tributylamine,dimethylbenzylamine, N,N,N′,N′ tetramethethylenediamine,1,2-dimethylimidazole, triethylenediamine, tetrabutyl titanate,tetrapropyl titanate, etc.

The adhesive may also be based upon liquid polysulfide prepolymerscomprising an oligomeric polysulfide terminated with thiol groups. Suchpolysulfides typically have the chemical structure: HS(R—S_(x))_(n)Hwhere x is either 1 or a small number of 2-4; x is an integer of 1 to 25and R is an alkylene, arylene or alkoxyalkylene, including, inparticular, —CH₂CH₂— and/or —CH₂(OCH₂CH₂)₂— often times further includedthe branching group —CH₂CHCH₂—. Preferred oligomeric polysulfides arethose based on the polyalkylene sulfides such as polyethylene sulphideand polypropylene sulfide as the polyarylene sulfides such aspoly(2,4-tolylene sulfide), poly(4,4′-biphenylene sulfide), andpoly(phenylene sulfide) (PPS). The thiol terminated oligomericpolysulfide may be polymerized or cured by reacting with epoxy orphenolic resins or compounds as well as with diisocyanates. Preferredpolysulfide adhesives can be formed by reaction of a thiol terminatedpolysulfide with a di- or polyfunctional epoxide such as the diglycidylether of bisphenol-A. Alternatively, the polymerization can be effectedby reaction of the terminal thiol groups with an olefin such as by thereaction with polyethylene glycol dimethacrylate. Curing agents forcurable polysulfides also include manganese dioxide, lead dioxide,antimony trioxide, and tellurium dioxide.

Further, the present invention is also applicable to adhesive andsealant compositions based upon silicone materials. These have asilicon-containing group which has a hydroxyl group or a hydrolyticallyunstable group bound to a silicon atom and can be crosslinked withformation of siloxane bonds. Suitable curing agents include tin octoate,lead octoate, and dibutyltin dilaurate. These curable compositions areparticularly useful as sealing compositions where weathering resistanceand heat resistance is important.

As noted above, the curable compositions may comprise mixtures ofmonomers, oligomers and/or prepolymers of the same general chemicalclass or of different classes so long as the systems are compatible andthe resultant cured or polymerized adhesive or sealant has efficaciousproperties. Where combinations or mixtures of monomers, oligomers and/orprepolymers are used, there are three mechanisms by which the secondarycomponent is incorporated with or into the composition of the primarycurable component. First, the second polymerizable component may have aplurality of reactive or functional sites for co-reacting orco-polymerizing with the first component. Second, the second componentmay have polar groups such as oxygen, amine, ether, ester, hydroxyl,ketone, epoxy or carboxyl, which form hydrogen bonds with the cured orpolymerized primary component. Third, the second component may be suchas to stericly entangle or hinder the movement of opposing chains of theprimary component.

Suitable secondary components which co-react or co-polymerize with theprimary curable component include, for example, allyl (meth)acrylates,alkene glycol di(meth)acrylates, alkyldiol di(meth)acrylates, alkoxyalkanol di(meth)acrylates, and trialkanol tri(meth)acrylates, especiallyallyl (meth)acrylate, triethylene glycol di(meth)acrylate, ethyleneglycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate,polyethylene glycol di(meth)acrylate, 1,4-butanediol di(meth)acrylate,diethylene glycol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate,neopentyl glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate,1,3-butylene glycol di(meth)acrylate, tripropylene glycoldi(meth)acrylate, ethoxylated bisphenol di(meth)acrylate, dipropyleneglycol di(meth)acrylate, alkoxylated hexanediol di(meth)acrylate,alkoxylated cyclohexane dimethanol di(meth)acrylate, pentaerythritoltri(meth)acrylate, and the like, and mixtures thereof. Of course othersuitable materials include those previously mentioned with respect toeach class of polymerizable component. Exemplary secondary componentshaving polar groups for forming hydrogen bonds include, for example,alkoxy acrylate, alkoxy methacrylate, polyester acrylate, polyestermethacrylate, acrylalkoxy phthalic acid, methacrylalkoxy phthalic acid,glycidyl methacrylate, glycidyl acrylate, cycloalkoxy acrylate,cycloalkoxy methacrylate, and the like. Finally, suitable secondarycomponents that result in steric entanglement or that stericly hinderthe movement of opposing chains of the forming adhesive polymer include,for example, alkyl (meth)acrylates of greater than 14 carbons,cycloalkyl (meth)acrylates, multicyclic alkyl (meth)acrylates, aralkyl(meth)acrylates, cycloalkoxy (meth)acrylates and the like. Specificexamples include stearyl acrylate, stearyl methacrylate, isobornylmethacrylate, benzyl acrylate, cyclohexyl methacrylate, and cetylacrylate.

Optionally, the curable compositions may further contain a terpeneresin, including, for example, wood rosin resins, esters of gum rosin,styrenated terpene, and terpene phenolic resins. Such terpene resinsfunction as tackifiers. Additionally, the adhesive strength of thecurable composition on oily metal sheets may be improved by theinclusion of liposoluble additives, such as limonene, dipentene, terpeneresins, or oil of turpentine, in an amount of 1-10 percent by weight,relative to the weight of the curable composition. Other optionalingredients include dyes, stabilizers, inhibitors, thickeners and thelike.

The foregoing sets forth but a brief overview of the myriad of curablecompositions to which the present invention is applicable and is notintended to be limiting to the aforementioned classes of curablecompositions nor to the specific polymerizable components mentionedtherein. And, of course, such compositions may optionally contain otheradditives such as dyes, pigments, plasticizers, stabilizers, solvents,surfactants, emulsifying agents and the like, as is well known to thoseskilled in the art. Additional curable compositions which can bemodified in accordance with the teaching of the present invention toprovide the benefits and attributes of the present invention are wellknow and readily recognized by those skilled in the art. Exemplarycurable compositions are further disclosed in, for example, Mahdi et.Al. (U.S. 20020010272), Bachmann et. al. (U.S. Pat. No. 3,814,156),Chernack (U.S. Pat. Nos. 4,940,852 and 4,808,639), Wallace (U.S. Pat.Nos. 4,428,982 and 4,081,012), Krieble (U.S. Pat. Nos. 3,489,599 and3,746,068), Newell (U.S. Pat. No. 4,252,708); Kropp et. al. (U.S. Pat.No. 6,573,328), Matsuo (U.S. Pat. No. 6,025,074); Fryd et. al. (U.S.Pat. No. 4,980,410); Azevedo (U.S. Pat. No. 4,417,028), Cooke et. al.(U.S. Pat. No. 4,497,916), Chao (U.S. Pat. No. 6,375,872); Usami et. al.(U.S. Pat. No. 5,397,812), Wolinski et. al. (U.S. Pat. No. 4,126,504),Siebert et. al. (U.S. Pat. Nos. 5,140,068 and 5,157,077), Deckert et.al. (U.S. Pat. No. 3,746,068), Hart et. al. (U.S. Pat. No. 4,536,524),Earls et. al. (U.S. Pat. No. 5,510,431), Hilbelink et. al. (U.S. Pat.No. 3,725,501), Sweeney (U.S. Pat. Nos. 4,830,558 and 4,555,206) andRich et. al. (U.S. Pat. Nos. 5,635,546 and 5,853,520), among others, allof which are hereby incorporated herein by reference.

The methods by which the curable compositions of the present inventionare prepared depend upon the form and method of application of thecurable composition itself. For liquid or thickened adhesive and sealantcompositions, the encapsulated carrier particles are merely blended intothe liquid curable composition by any of the known and commerciallyemployed techniques. Preferably such compositions are thickenednaturally or by the addition of suitable thickening agents and/orthixotropic materials such as fumed silica, so that the encapsulatedcarrier particles do not settle out during storage. Alternatively, suchcurable compositions should be shaken or stirred prior to application ofthe same.

Where the curable compositions are to be employed in a pre-appliedmanner, i.e., applied to a substrate in stock form and stored prior touse, e.g., applied to nuts or bolts at a factory or site of conversionfor subsequent use at another location, the encapsulated carrierparticles will be dispersed in the liquid curable component, applied tothe substrate and a polymer film, which may be derived from the liquidcurable composition, formed thereon or, preferably, the liquid curablecomponent is also encapsulated and both the encapsulated liquid curablecomponent and the encapsulated carrier particles are dispersed in asuitable binder which is used to adhere the capsules to the substrate.With the former, following application of the liquid curable compositionof the present invention to a substrate, a thin film of a liquidpolymerizable material or a solution of a film forming material isapplied so as to cover the underlying liquid curable composition therebyencasing or enveloping the liquid curable composition between the filmand the substrate. It is also possible that the protective film may bederived from the curable composition itself. In this instance, thecurable composition also contains a suitable photoinitiator and/orphotosensitizer whereby, upon exposure to the appropriate radiation,preferably UV light, surface cure of the liquid curable component isinitiated. Such curable compositions may also contain an appropriate UVscreening agent to ensure that only a thin, surface film of materialcures or polymerizes. Such systems are taught in or readily derived fromthe teachings of Ozono (U.S. Pat. No. 4,588,639) and Wallace (U.S. Pat.No. 4,428,982), herein incorporated by reference, among others and arewell known to those skilled in the art.

Typically, however, and preferably, both the liquid curable componentsand the curative therefore will be encapsulated and the microcapsulesdispersed in an appropriate binder. The choice of the binder will bedictated by the composition of the wall material and the composition ofthe substrate. The binder system may be a curable binder system usingthe same or similar curable or polymerizable materials as are useful forforming the shell wall and/or the adhesive or sealant. Suitable curablebinder systems include those based on the reaction of an anhydride andarylenes, alkylenes, alkoxylenes, alkarylenes, aralkylenese,alkoxyalkylenes, aryloxyalkylenes and aryloxyarylenes. Suitable bindersalso include water-soluble binding agents such as polyvinyl alcohol,styrene-maleic anhydride copolymers and gelatin as well as solventsoluble binding agents such as chloroprene, polyester acrylates,urethane acrylates, carboxyl- or hydroxy-modifiedvinylchloride-vinylacetate copolymer, cellulose actetate, epoxides,polyterpenes, hydroxypropylcellulose, hydroxyethylcellulose, sodiumcarboxymethylcellulose, poly(glycolic acid), poly(lactic acid),copolymers of the foregoing, poly(aliphatic carboxylic acids),polycaprolactone, poly(acetals), poly(lactic acid-caprolactone),poly(glycolic acid-caprolactone), polyanhydrides, albumin, casein,butyrate resins, polyvinylacetate, polyesters of dibasic acids anddiols, polyvinylchloride, polyvinylbutyral, polyvinyl formal,varnish-based and tar-base resins, and waxes and the like. Organicsolvents for the latter include chlorinated solvents such astrichloroethylene, trichloroethane, methylenechloride;chlorinated/fluorinated hydrocarbons solvents such asmonofluorotrichloroethane and dichlorodifluoroethylene; hydrocarbonsolvents such as hexane, and pentane; alcohols such as ethanol andisopropanol, and lacquer solvents such as methyl ethyl ketone, toluene,and benzene. Additional binder systems are disclosed in, for example,Park et. al. (U.S. Pat. No. 5,827,924), Matsuo (U.S. Pat. No.6,025,074), and Bachmann et. al. (U.S. Pat. No. 3,814,156), hereinincorporated by reference and elsewhere and are well known to thoseskilled in the art.

Particularly desirable binder systems are those that arephotopolymerizable, i.e., cure or polymerize upon exposure to light,preferably UV light. Such binder systems may comprise any of theabove-mentioned free-radically curable monomers, oligomers and/orpre-polymers and an appropriate photoinitiator therefore and/or aphotosensitizer. Suitable photoinitiators include, among others, benzoinand its derivatives, benzophenones and their derivatives, xanthones,benzyl, benzilketals (especially benzildimethylketal), acetophenones andtheir derivatives (especially α,α-diethoxyacetophenone),α-hydroxyalkylphenones, o-acyl-α-aminoketones, acylphosphine oxides(especially 2,4,6-trimethylolbenzoyldiphenyphosphine oxide) andacylphosphonates. Additional photoinitiators include substitutedpyrylium salts or anthracene and derivatives thereof, e.g., substitutedanthracenes, or anthraquinone or ketocoumarine derivatives.Photoinitiators are typically used in an amount within the range ofabout 0.5% to about 10% by weight based on the weight of the bindercomposition, with about 2% to about 4% or greater by weight of the totalbinder composition being desirable. Alternatively or in addition, thephotopolymerizable binder may include a photosensitizer. Suitablephotosensitizers include benzophenone or dyes like eosin, fluorescein,thiazole dyes, thiazine dyes, oxazine dyes, azine dyes, aminoketonedyes, xanthene dyes, acridinium dyes or phenazine dyes. Inclusion ofsuch photosensitizers often lessens the intensity and/or duration ofexposure to the radiation used to initiate cure. As a general guide, forphotoinitiated polymerizations, it is also desirable to use aphotoinitiated radical generating component, such as peroxides,peresters, azo compounds and derivatives, benzoin derivatives,alpha-halo acetophenones, or acylphosphine oxides, in an amount withinthe range of about 0.005% to about 4% or greater (desirably within therange of about 0.01% to about 1.5%) by weight of the total bindercomposition. Though the foregoing discussion has been primarily withrespect to free-radical photopolymerization, it is also understood thatsuitable binder systems may be photoionically activated as well.Suitable cationic photoinitiators include the iodonium salts, especiallythe diaryliodonium salts. Such iodonium salts are described in U.S. Pat.Nos. 3,729,313; 3,741,769; 3,808,006; 4,250,053 and 4,394,403. Theiodonium salt can be a simple salt, containing an anion such aschloride, bromide, iodide, antimony pentafluoride or arsenichexafluoride or the like. Mixtures of iodonium salts can be used ifdesired. Typically the iodonium cationic photoinitiators are used incombination with a sensitizer and an electron donor compound.Accordingly, selection of a particular iodonium salt may depend to someextent upon the particular polymerizable component, sensitizer and donorchosen.

The binder compositions may also include other ingredients includingcuratives and additives for the adhesive or sealant composition providedthat in the case of curatives, the curative contained in the binder isnot such that premature rupture of the microcapsules containing thecurable components of the curable compositions will allow prematurecuring or polymerization thereof. Thus, for example, an accelerator maybe dispersed in the binder so long as the initiator for the givencurable composition is in the encapsulated carrier or anotherencapsulated component of the curable composition.

The amount of the encapsulated cure system to be incorporated into oremployed with the curable composition depends upon a number of differentparameters including the type of curable composition, i.e., whether itis an addition polymerizable system or a step growth polymerizationsystem; the state of the curable composition, i.e., whether it is aliquid system or a fully encapsulated system that is applied in abinder, the degree of polymerization or cure desired; the amount and/orstoichiometry of the curable components, the amount of curative in thecarrier particles, and the like. Those skilled in the art will readilyrecognize or be able to determine the proper level of incorporation.Most often one would employ that amount of the encapsulated cure systemwhich contains the same amount of curative as would be employed were thecarrier not present.

In the case of the pre-applied adhesive and sealant compositions, theamount of the encapsulated cure system to be incorporated into thebinder system also is influenced by the method and rate of applicationof the pre-applied composition as well as the composition of the binder.Binder compositions comprising a binder polymer in solution willgenerally have lower levels of the encapsulated components (both curesystems and curable components) than liquid curable binder systems basedon the total weight of the binder system. Typically it is preferred tominimize the amount of the binder material while concurrently maximizingthe amount of the encapsulated components (again cure systems andcurable components) to allow for optimal bond or seal capabilities.Generally speaking, the amount of the encapsulated cure system to becombined with the other microencapsulated components will be consistentwith that level used with conventional encapsulated adhesive and sealantcompositions. However, it is also believed that lower levels may beemployed due to the higher degree of or more efficacious mixing of thecurative with the curable composition during activation.

The curative within the encapsulated cure system of the presentinvention is released and/or made available by high shear, especiallyhigh shear mixing which masticates or kneads the carrier or, in the caseof a carrier which flows upon exposure to heat, moderate shear mixing.The specific method by which this occurs depends upon the carrier,whether the encapsulated cure system is part of a liquid adhesive orsealant composition or part of a pre-applied adhesive or sealantcomposition and, in the latter instance, the nature of the substrate towhich the preapplied material is applied. For example, for liquidcurable compositions comprising the encapsulated cure system, cure ofthe curable composition may be effected by dispensing or applying thecurable composition through a mixer nozzle which employs a high shearmixing element or an element similar to a screw in an extrusion barrel.Alternatively, a bead of the liquid curable composition containing theencapsulated carrier therein may be laid upon a substrate and subjectedto mixing or mastication with a mixer blade or series of blades. Thelatter may also be in the form of a plurality of stationary dams whereinas the substrate with the bead thereon, passes the dams, the dams act tomove and knead the bead so as to expose the curative and allow intimatemixing thereof with the components of the curable composition.

Where the carrier in the liquid curable composition is a hot melt, a waxmaterial or a heat sensitive material, the nozzle will have a heatingelement in combination with a mixer element, which may or may not behigh shear mixer element, whereby the carrier is transformed to asoftened or flowable state by the heat generated by the heating element.Alternatively, in following with the last sentence of the precedingparagraph, the blade and/or dams may be heated so the heat sensitivematerial is rendered pliable and/or flowable concurrent with the mixingwith the curable composition.

In the case of preapplied adhesive or sealant compositions, the cure orpolymerization of the curable composition may be effected by a mixerblade which is repetitively passed through or across the preappliedcurable composition. In high-speed industrial process, the adhesive maybe passed by a stationary or reciprocating blade or mixer element, whichmay or may not be heated. In the case of a stationary element, theelement may itself comprise a series of dam-like structures that actsimilar to a plow, pushing and mixing the pre-applied curablecomposition as it is scraped from the substrate surface. In bothinstances, because the adhesive mix has a high viscosity, due largely tothe carrier component and/or the presence of thickening or viscosityenhancing additives, the initiated curable composition passing from themixer portion is often in the form of raised ridges so that when twosubstrates are brought into contact with the initiated curablecomposition, the same will contact both substrate surfaces: thus,filling the gap, especially between uneven substrate surfaces.

The key aspect of the mixer element is that it kneads or masticates thecurable composition so as to ensure rupture of the shell wall and, moreimportantly, repeated mashing or kneading of the carrier so as to exposemore and more of the entrained curative.

As noted above, because of the high viscosity of the activated adhesiveand sealant compositions, it is possible that the same may be applied asor, depending upon the means by which the composition is activated,arise from the activation step as a raised bead or plurality of beads ofthe activated material. This characteristic enables one to apply a thinfilm of the pre-applied adhesive to a given stock material which is thenstored for subsequent use. Because the adhesive is applied in a thinlayer, the stock materials may be stacked high without concern thatadhesive on one end will cause a stack to lean and fall over. While somestock materials already have thin films of a reactivatable adhesivematerial applied to their surface, the thickness of the bond is limitedto the thickness of the pre-applied reactivatable adhesive film. In thepresent invention, however, because of the physical and rheologicalproperties of the activated adhesive and sealant compositions, one isable to make raised beads of the same so that uneven surfaces and gapscan be accommodated. Applications which conventional pre-applied filmscannot address.

The following non-limiting working examples exemplify and provideadditional scope and understanding to the present invention.

Encapsulated Cure Systems

A number of novel encapsulated cure systems (hereinafter also referredto as “ECS”s) according to the practice of the present invention weremade in a multi-step process which involved the preparation of theinternal phase of the ECS microcapsules, i.e., the carrier material or,if the carrier were to be polymerized in-situ, the precursors thereforeand the curative contained therein, followed by one or more wall formingor encapsulation steps. Generally speaking, the internal phase wasprepared by adding the plasticizers, polymeric thickeners and/ortackifier resins to the polymerizable monomer in an appropriate vesselor beaker and stirring the combination at room temperature until allsolids were dissolved in the monomer. Thereafter, the more thermallysensitive components, especially the curatives to be incorporated intothe carrier, e.g., the peroxide and azo initiators, were then added tothe mixture under constant agitation or mixing and at an elevatedtemperature, generally 45° C., until all solids were fully dissolved, orsubstantially so. The first mixing step was performed at roomtemperature as dissolving the resin in the monomer does not appear to betemperature dependent and is quite lengthy. On the other hand, themixing of the curatives is more temperature dependent and, thus, herethe elevated temperature is preferred. Of course, one could add allingredients at an elevated temperature and in a different sequence;however, due to the slow rate at which the resins dissolve in themonomer, such higher temperatures for extended periods may adverselyaffect the potency or efficacy of the curatives.

Encapsulation of the ECS internal phase was accomplished by a one-, two-or three-phase, multi-step process, preferably, the two-phase,multi-step process. Unless otherwise indicated, all encapsulationprocesses were conducted in a jacketed steel vessel or reactor under anitrogen blanket having integrated agitation means for ensuring goodmixing of the components therein. The two-phase encapsulation processinvolved the following general steps:

-   -   An intimate mixture of a colloidal polyacrylic acid (C-121 . . .        ), sodium hydroxide (5% solution) and water was prepared in the        reaction vessel.    -   Thereafter a partially methylated methylol melamine resin        solution (Cymel 385) was added to the above mixture under        constant agitation. Due to the high viscosity of this material,        its addition was typically accomplished over a four-minute        period.    -   Following completion of the addition of the melamine resin, the        ECS internal phase material was then added to the mixture under        constant agitation.    -   Once the ECS internal phase material was intimately mixed in,        generally after about 16 minutes or so, the reaction mix was        subjected to high shear conditions at room temperature or,        preferably, at a slightly elevated temperature to achieve the        desired particle size for the droplets of the ECS internal phase        material. High shear or emulsification conditions were achieved        by the use of an integrated or inserted impeller mechanism.        Particle size determinations were made periodically to assess        the progress of the emulsification.    -   Shortly before the completion of the emulsification process,        generally about five minutes before, the wall forming        composition for the second phase encapsulation process was        prepared. As before, the second phase wall forming composition        was prepared by adding the partially methylated methylol        melamine resin to a mixture comprising the colloidal polyacrylic        acid, sodium hydroxide and water.    -   Approximately five minutes following cessation of the        emulsification process, the prepared second phase wall forming        composition was added to the mixture, which, all the while, is        maintained under constant agitation.    -   Following the addition of the second phase wall forming        composition a salt, preferably sodium sulfate, was then added to        the mixture to complete the encapsulation process.    -   Thereafter, the temperature of the reaction mix was gradually        elevated to the desired reaction temperature over a period of        about two hours or less, preferably about an hour or less, and        maintained at the elevated temperature for an extended period of        time to ensure complete formation of the capsule walls as well        as polymerization of the ECS internal phase materials.

Obviously, the foregoing sequence is but one of many that could beapplied to the practice of the present invention and those skilled inthe art will readily recognize that many modifications and variationsthereto could also be employed successfully. For example, the wallforming material and the ECS internal phase materials could be addedconcurrently or in reverse sequence. However, the specified sequence isespecially desirable as it is believed that the wall forming materialmay aid in the emulsification process of the internal phase materials.Furthermore, the timing of the emulsification process will varydepending upon a number of factors including the type, size and shape ofthe impeller blade itself, and the speed of the same. While higher shearprovides for smaller particle size, those skilled in the art willreadily recognize that after a given point in time, continued high shearmixing will not lead to any further material change in particle size.Particle size determinations were made during and following theencapsulation process using an Accusizer model 780 particle sizeinstrument made by Particle Sizing Systems.

EXAMPLES 1-19

A number of different microencapsulated novel activator systemsaccording to the practice of the present invention were prepared. Ineach of these examples the carrier was polymerized in-situ concurrentwith or following encapsulation. The formulations of the internal phaseof the ECS microcapsules were as shown in Table 2, all amounts arepresented in grams. Except as indicated below, the ECS microcapsuleswere prepared in accordance with the aforementioned two-phaseencapsulation process using the cell forming materials of Table 3 underthe reaction conditions and times of Table 4. Table 4 also sets forththe physical attributes, namely the average particle size and cell wallcontent, of the microcapsules formed.

TABLE 1 Materials Guide Tradename Acronym Chemical Description SourceCompany Acrysol TT-615 acrylic alkali thickener Rohm & HaasPhiladelphia, PA C-121 PAA polyacrylic acid colloid solution RhonePoulenc Marrietta, GA CHP cumene hydroperoxide Atofina ChemicalsPhiladelphia, PA CN551 amine modified polyether acrylate oligomerSartomer Company Eaton, PA CN501 amine modified polyether acrylateoligomer Sartomer Company Eaton, PA CN2404 metallic acrylate oligomerSartomer Company Eaton, PA Cycat 500 sulfonic acid catalyst CytecIndustries West Patterson, NJ CYM M-100 3,4-epoxycyclohexylmethylmethacrylate Daicel Chemical Cymel 385 partially methylated methylolmelamine resin sol'n Daicel Chemical West Patterson, NJ CALFAX DBA-70dodecyldiphenyloxide disulfonic acid Pilot Chemicals Sante Fe Springs,CA DEGDMA diethylene glycol dimethacrylate Disparlon 6650 polyamidethixotropic agent King Industries Norwalk, CT DNNDSA dinonyl naphthalenedisulfonic acid EHDMAB ethylhexyl dimethylamino benzoate Escorez 5300hydrogenated hydrocarbon resin Exxon Mobil Houston, TX Indopol H-100polybutene resin plasticizer Innovene Naperville, IL Indopol H-300polybutene resin plasticizer Innovene Naperville, IL Indopol H-1900polybutene resin plasticizer Innovene Naperville, IL I6-B red carbonlesscoloring agent Jayflex DIOP di-isooctyl phthalate Exxon Mobil Houston,TX Jonacryl 3050 styrene acrylic latex emulsion Johnson PolymerSturtevant, WI K-702 polyacrylic acid Noveon Cleveland, OH Luprox A-75(75% BPO) benzoyl peroxide Atofina Chemicals Philadelphia, PA Luprox Pt-butyl peroxybenzoate Atofina Chemicals Philadelphia, PA MEHQ methylethyl hydroquinone Norpar 12 aliphatic hydrocarboin fluid Exxon MobilHouston, TX Norsolene A-110 aliphatic modified C-9 hydrocarbon resinSartomer Company Eaton, PA Norsolene A-90 aliphatic modified C-9hydrocarbon resin Sartomer Company Eaton, PA Norsolene S-105 aromatichydrocarbon resin Sartomer Company Eaton, PA Norsolene S-85 aromatichydrocarbon resin Sartomer Company Eaton, PA PHZBSApara-hydrazinobenzene sulfonic acid PHBSA para-hydroxybenzene sulfonicacid PVA polyvinylalcohol SR213 BDDA 1,4-butanediol diacrylate SartomerCompany Eaton, PA SR238 HDDA 1,6-hexanediol diacrylate Sartomer CompanyEaton, PA SR256 EEEA 2-(2-ethoxyethoxy)-ethyl acrylate Sartomer CompanyEaton, PA SR257 SA stearyl acrylate Sartomer Company Eaton, PA SR295PETTA pentaerythritol tetraacrylate Sartomer Company Eaton, PA SR351TMPTA trimethylolpropane triacrylate Sartomer Company Eaton, PATMPTA/I6-B 1% I6-B in SR351 SR355 DTMPTTA di-trimethylolpropanetetraacrylate Sartomer Company Eaton, PA SR399 DPEPA dipentaerythritolpentaacrylate Sartomer Company Eaton, PA SR440 IOA iso-octyl acrylateSartomer Company Eaton, PA SR444 PETA pentaerythritol triacrylateSartomer Company Eaton, PA SR495 CLA caprolactone acrylate SartomerCompany Eaton, PA SR506 IBA isobornyl acrylate Sartomer Company Eaton,PA SR604 PPGMMA polypropylene glycol monomethacrylate Sartomer CompanyEaton, PA Sarcure SR1135 photoinitiator Sartomer Company Eaton, PASylvares ZT105LT styrenated terpene resin Arizona Chemical Jacksonville,FL Sylvalrte RE 105L resin ester tackifier Arizona Chemical Tinuvin 234benztriazole UV absorber Ciba Specialty Chemicals Tarrytown, NY Tinuvin328 benztriazole UV absorber Ciba Specialty Chemicals Tarrytown, NYTT-615 polyacrylate Rohm & Haas Philadelphia, PA Vazo 52 2,2′-azobis(2,4-dimethyl valeronitrile) DuPont Wilmington, DE Wingtak 10 liquidhydrocarbon tackifier Goodyear Chemical Beaumont, TX

TABLE 2 Examples 1–19 Internal Phase Composition Example 1 2 3 4 5 6 7 89 10 iso-octyl 123 187 110 263.6 291.8 62.5 107.2 144 140 49.5 acrylatePPGMMA 14.55 131.8 145.9 50 15 2.5 10 25 stearyl 131.8 145.9 37.5 75acrylate TMPTA 2.5 0.5 2.03 2 1.16 4.5 3.5 0.5 ion 5 20 exchange resintriacetin Sylvares 125 50 ZT105LT Sylvalite 100 RE 105L Norsolene 100A-110 Norsolene A-90 Norsolene 100 350 400 103 S-105 Norsolene 100 S-85Escorez 100 5300 Indopol 12.5 29.12 H-300 methyl palmitate di(iso-octyl)phthalate Luprox 35 40 33.3 10.3 40 33.3 33.3 A-75 (75% BPO) benzoyl 4 5peroxide Luprox P cumen 30 105 120 60 hydroperxide Vazo 52 0.5 PHZBSAEDMAB total wt. 254 255 291.2 1019 1165 283.3 300 290 283 283 (grams)Example 11 12 13 14 15 16 17 18 19 iso-octyl 75 50 401.9 104 103 88.5acrylate PPGMMA 49 50 58.2 15 14.6 15 stearyl 100 150 75 100 50 acrylateTMPTA 1 8.12 2.7 2.04 2.1 ion 20 exchange resin triacetin 15 SylvaresZT105LT Sylvalite RE 105L Norsolene 100 100 100 A-110 Norsolene 100 A-90Norsolene 100 400 103 100 103.5 S-105 Norsolene S-85 Escorez 5300Indopol 116.5 29.1 30 H-300 methyl 50 palmitate di(iso-octyl) 30phthalate Luprox 33.3 33.3 33.3 33.3 33.3 40 10.3 18 A-75 (75% BPO)benzoyl peroxide Luprox P 27 cumen 120 60 hydroperxide Vazo 52 9.76PHZBSA 5.16 EDMAB 2.33 total wt. 283 283 283 283 283 1165 300 291 299.1(grams)

TABLE 3 Examples 1–19 Cell Wall Materials Example 1 2 3 4 5 6 7 8 9 1011 12 13 14 15 16 17 18 19 Cell wall Phase I Cymel 385* 4 4 10 35 40 610 12 6 6 6 6 6 6 6 40 10 10 10 C-121 5 5 22 70 88 7 22 7 7 7 7 7 7 7 788 22 22 23 sodium 2 2 20 27.6 80 5.5 11 6 4 5.5 5.5 5.5 5.5 5.5 5.5 8026 20 12.5 hydroxide (5%) sodium 32 sulfate water 163 163 275 875 100250 275 250 250 250 250 250 250 250 250 1000 245 275 275 Cell wall PhaseII Cymel 385 24 12 25 87.5 100 16 25 12 18 18 18 16 18 18 18 100 25 2525 C-121 5 5 5 17.5 20 7 5 7 7 7 7 7 7 7 7 20 5 5 5 sodium 0.5 0.5 2.5 16 3 2.5 2.5 2.5 2.5 2.5 2.5 0.8 hydroxide (5%) sodium 3 3 8 28 32 4 8 44 4 4 4 4 4 4 8 8 8 sulfate water 300 300 100 245 280 50 100 75 25 50 50150 50 50 50 200 70 100 100

TABLE 4 Examples 1–19 Encapsulation Process Example 1 2 3 4 5 6 7 8 9 10Milling temp (° C.) 25 25 25 45 45 45 45 45 45 45 Time (min) 75 75 24 1515 75 17 45 75 75 Rate (rpm) 1100 1100 2800 1750 1800 2000 2250 1000 9001500 Ramp up of Reaction intial temp 25 25 25 45 45 45 45 45 45 45 (°C.) end temp 90 90 45 68 68 65 68 65 65 65 (° C.) time (hrs)** 2 2 XX XXXX XX XX XX XX XX Reacting temp 90 90 45 68 68 65 68 65 65 65 (° C.)time (hrs) 16 16 0.17 8 8 8 8 8 8 8 Secondary Reaction temp 80 (° C.)time (hrs) ONT* Average microcapsule size (microns) 47 34 19 9 13 18 2936 64 37 weight 7.9 4.7 8.4 8.5 8.4 5.9 8.2 6.2 6.4 6.4 percent cellwall Example 11 12 13 14 15 16 17 18 19 Milling temp (° C.) 45 45 45 4545 45 45 25 Time (min) 75 75 75 75 75 35 30 25 Rate (rpm) 2400 1500 12002000 2400 1750 2650 2400 Ramp up of Reaction intial temp 45 45 45 45 4545 45 25 (° C.) end temp 65 65 65 65 65 65 68 65 (° C.) time (hrs)** XXXX 1 1 1 XX XX XX Reacting temp 65 65 65 65 65 65 68 65 (° C.) time(hrs) 8 8 8 8 8 8 8 6 Secondary Reaction temp 80 (° C.) time (hrs) 6Average microcapsule size (microns) 31 73 58 34 17 19.5 22 32 weight 6.46.4 6.4 6.4 6.4 XX 8.2 8.4 percent cell wall *ONT—overnight **unlessindicated, generally about 1 hour or less.

Unlike the other examples of this series, Example 3 employed a two-stageheat cycle in bringing the final reaction mix to the final reactiontemperature. Specifically, as indicated in Table 4, the reaction mix wasinitially elevated to a temperature of 45° C. and held at thattemperature for a period of ten minutes following which it was thenelevated to 80° C. and held at that temperature overnight to allow theinternal phase materials to polymerize.

In Example 8, the ECS internal phase was added to the wall formingpre-mix of polyacrylic acid, sodium hydroxide and water and emulsifiedfor a period of 45 minutes after which the wall forming melamine resinwas added and the mixture emulsified for an additional 30 minutes.

Finally, Example 18 employed a two-stage carrier polymerization whereinthe initial stage was conducted at 65° C. for a period of 6 hours, asindicated in Table 4, following which the temperature was elevated to80° C. and the reaction continued for another 6 hour period.

EXAMPLES 20-22

A second series of examples was prepared again using a two-phaseencapsulation process except that no polymerizable wall formingmaterials were added during the second phase. As seen in Table 5, whichsets forth the composition of the ECS internal phase as well as thecomponents of the wall forming materials, the second phase of theencapsulation process merely added a solution of sodium hydroxide andsodium sulfonate in water. The reaction conditions and the physicalattributes of the microcapsules formed were as set forth in Table 6. Asseen in Table 6, Example 22, like Example 18 above, employed a two-stagecarrier polymerization except here the initial polymerization stage wasconducted at 65° C. for a period of 6 hours followed by a second stagewherein the reaction temperature was elevated to and maintained at 90°C. for a period of 16 hours.

EXAMPLES 23-25

Example 23 and Examples 24 and 25 demonstrate alternate encapsulationprocesses wherein encapsulation was achieved through a single phase ortriple phase encapsulation process, respectively. The composition,processs of production and resulting ECS microcapsule properties were asshown in Tables 5 and 6.

TABLE 5 Examples 20–25 Internal Phase and Cell Wall Materials Example 2021 22 23 24 25 Carrier iso-octyl acrylate 74 74 75 124.3 149.3 PPGMMA37.5 38 37.5 37.5 isodecyl acrylate 74 stearyl acrylate 37.5 38 37.537.5 TMPTA 1 1 1 0.75 DEGDMA 0.75 Sylvares ZT105LT 125 100 NorsoleneS-105 87.5 88 87.5 100 Indopol H-300 12.5 12.5 Indopol H-1900 13 LuproxA-75 (75% 33.3 33 33.3 33.3 20 33.3 BPO) cumen hydroperxide 15 15 15 10Cycat 500 7 CALFAX DBA-70 4 4.9 DNNDSA 5 wt. (grams) 302.3 305 303 298.3270 283.3 Cell wall Phase I Cymel 385 32 24 21.4 24 4 6 C-121 14 14 10.714 5 7 sodium hydroxide 13 14 15 10 2.5 5 (5%) sodium sulfate 4 water250 250 250 300 163 275 Cell wall Phase II sodium hydroxide 5 5 6.15 1 5(5%) sodium sulfate 4 4 4 water 95 70 95 5 15 Cell wall Phase III Cymel385 4 6 C-121 5 7 sodium hydroxide 1 5 (5%) sodium sulfate 3 4 water 16350

TABLE 6 Examples 20–25 Encapsulation Process Example 20 21 22 23 24 25Milling temp (° C.) 45 45 45 45 45 45 Time (min) 75 75 75 75 75 75 Rate(rpm) 1000 1750 1250 3000 1100 1100 Ramp up of Reaction intial temp (°C.) 45 45 45 45 45 45 end temp (° C.) 65 65 65 65 65 65 time (hrs)* XX 1XX 1 1 XX Reacting temp (° C.) 65 65 65 65 65 65 time (hrs) 8 8 8 8 8 8Secondary Reaction temp (° C.) 90 time (hrs) 16 Average microcapsulesize (microns) 19 21 17 12 65 55 weight percent 7.8 6 5.5 6.1 2.3 3.3cell wall *time not recorded, though about 1 hour or less.Adhesive Compositions

In order to demonstrate the efficacy and utility of the encapsulatedcure systems of the present invention, a number of curable adhesiveformulations were prepared incorporating several of the foregoingencapsulated carrier systems. Example 26 employs an ECS microcapsule ina one-part, liquid adhesive composition whereas the remaining examplesall demonstrate the use of ECS microcapsules in a pre-applied adhesiveformulation wherein the ECS microcapsule, an encapsulated curablecomposition (hereinafter also referred to as an “ECC”) were combined ina binder system and applied to various substrates, allowed to dry or, asappropriate, cure, and subsequently activated.

Table 7 sets forth the internal phase of the various microcapsulescontaining the curable compositions as well as the make-up of the wallforming materials used in encapsulating the same. Generally, the processby which the ECC microcapsules were formed was as follows:

-   -   the components for the ECC internal phase were mixed under        nitrogen blanket until all components were dissolved and held        for subsequent use;    -   all components of the cell wall phase I, excluding the melamine        resin, were added to a steel reactor at 25° C. and mixed under        low shear, i.e., 300 rpm; thereafter the melamine resin was        added and mixed at low shear for an additional 4 minutes.    -   the prepared ECC internal phase formulation was then added to        the reactor and intimately mixed at 300 rpm for an additional 16        minutes;    -   the mixture was then subjected to high shear emulsification of        3000 rpm at 25° C. for 75 minutes. During this time, the second        phase wall forming materials were prepared with the melamine        being added to the remaining components of the second phase wall        composition about five minutes prior to the completion of the        emulsification step of the aforementioned reactor mix;    -   once the emulsification was completed, the mixture in the        reactor was continually mixed with a flat paddle mixer at low        shear, i.e., 300 rpm,    -   approximately five minutes following cessation of the        emulsification step, the second wall forming composition was        added to the mixture followed by the sodium sulfate, if used;

TABLE 7 Curable Capsules A–K Curable Capsule A B C D E F G H I J KInternal Phase butyl ferrocene 5 25 5 ferrocene 10 50 10 10 10 TMPTA 2451100 212.5 DTMPTTA 220 PPGMMA 25 12.5 62.5 12.5 12.5 12.5 12.5 12.5PETTA 220 PETA 220 228.13 268.5 233.75 TMPTA/I6-B 1212.5 217.5 MEHQ 1252.5 EHDMAB 1.88 CHP 30 PHBSA 1.5 tetramethyl analine 3.75 Disparion 66507.5 Tinuvin 234 3.75 18.75 3.75 3.75 3.75 3.75 Tinuvin 328 3.75 18.753.75 3.75 3.75 3.75 Cell wall Phase I Cymel 385* 4 70 14 14 70 14 14 1414 16.34 14 C-121 5 25 5 5 25 5 5 7.5 30 K-702 25.65 5 sodium hydroxide(5%) 2.5 1100 2.25 2.25 11.25 2.25 2.25 3.85 17.1 sodium hydroxide (20%)8.19 1.5 sodium sulfate 3 3 3 5 water 163 815 163 163 815 163 163 163275 291.75 163 Cell wall Phase II Cymel 385 24 70 14 14 70 14 14 14 1416.34 C-121 5 25 3 5 25 5 5 5 5 K-702 5.84 5 sodium hydroxide (5%) 1.575 1 1 5 1 1 0.85 0.8 sodium hydroxide (20%) 1.04 0.85 sodium sulfate 315 3 15 3 3 3 water 163 500 100 100 500 100 100 75 100 116.7 100 Cellwall Phase III Cymel 385 22.4 C-121 8.75 sodium hydroxide (5%) 0.9sodium sulfate 3

-   -   thereafter, the reactor temperature was gradually raised to        65° C. over about two hours and the reaction mix maintained at        65° C. with low shear mixing for an additional 8 hours before        the ECC microcapsules were recovered.

Although several of the pre-applied microencapsulated adhesivecompositions employed aqueous based binders, several employed UV curablebinder systems. The compositions of the various UV binder systems usedin the following examples were as set forth in Table 8. These binderswere prepared under ambient conditions, with care to preclude exposureto UV light, using traditional mixing equipment.

EXAMPLE 26

A one-part liquid curable adhesive composition was prepared by mixingtogether 6.7 parts by weight tetramethyl analine, 33.3 parts by weightof the encapsulated cure system prepared in accordance with Example 19and 60 parts by weight of dipentaerythritol pentaacrylate (SartomerSR399). A think film of the liquid adhesive composition was applied toan aluminum plate (0.75″ by 4″) and another aluminum plate placed overthe same. The plates were rubbed together using about a one inchmovement, while applying finger pressure, about 10-20 times. Thereafter,the assembly was allowed to stand for 5-10 seconds following which itwas found that the assembly could not be separated, indicating that theadhesive had cured.

EXAMPLE 27

An aqueous based pre-applied adhesive composition was prepared by mixingtogether 4 parts by weight of a water solution containing 5% by weightpolyvinyl alcohol and 5% by weight benzoyl peroxide, 2 parts by weightp-toluene sulfonic acid (p-TSA), 20 parts by weight of ECC microcapsuleA, and 74 parts by weight of the encapsulated cure system prepared inaccordance with Example 1. A piece of chipboard was pretreated with acoating of a 5% solution of polyvinyl alcohol using a #16 rod. Thetreated surface was then coated with the adhesive composition using a#50 rod. The coating was allowed to dry and then activated manuallyusing a razor blade by stoking the edge of the blade with hand pressurequickly across the pre-applied adhesive 10 times. The chipboard was thenfolded on itself and held under hand pressure for 10 seconds. Thechipboard remained bonded following release of the hand pressure.

EXAMPLE 28

A second aqueous based pre-applied adhesive composition was prepared bymixing together 15 parts by weight of styrene acrylic latex emulsion(Jonacryl 3050), 3.5 parts by weight sodium bicarbonate, 0.4 parts byweight polyacrylates (TT-615—Rohm & Haas), 52 parts by weight of theencapsulated cure system prepared in accordance with Example 6, 14.2parts by weight of ECC microcapsule B and 14.2 parts by weight of ECCmicrocapsule C. The composition was applied as a thin film (0.006″) tothe clay side of clay-coated news back stock. The coating was allowed todry and then activated manually using a razor blade by stoking the edgeof the blade with hand pressure quickly across the pre-applied adhesive10 times. The news back stock was then folded on itself using fingerpressure to mimic the closure of a cereal carton flap. The news backstock remained bonded following release of the hand pressure and wasfound to have a strong bond when pulled apart after one minute. Fibertear was observed upon pulling apart assemblies allowed to cure for 5minutes and one hour.

EXAMPLES 29-36

A series of pre-applied adhesive compositions in UV curable binders werealso evaluated employing the encapsulated cure system of the presentinvention. The make-up of these pre-applied compositions were as setforth in Table 9, with the composition of the encapsulated curablecomposition (ECC) as set forth in Table 7, the composition of specificBinder System as set forth in Table 8 and the selection of theencapsulated cure system (ECS) as identified by the therein statedexample number, e.g., ECS Cap 5 means the encapsulated cure system asprepared in Example 5.

In each of these examples, the adhesive composition was applied as athin film strip, 0.5″ wide by 0.006″ thick along the centerline of themajor axis of 3″ wide by 5″ long cards cut from paperboard cereal boxstock. The adhesive was applied to the fiber side of the cards and curedunder UV light. The adhesive was activated and the card bonded to a likecard using a custom-made activator apparatus. The apparatus comprised aninsertion station, an activator station and a bonding station with arail extending from the insertion station, through the activationstation and ending at the bonding station and a sled movable along therail. In testing the prepared samples, a card with the adhesivepre-applied thereto is set on a sled, which is equipped with a vacuum,adhesive side up, with the major axis parallel with that of the rail.The sled then traverses along the rail at a rate of between 150 and 250feet per minute, through the activator station where a stationaryactivator means having a face with one or more ridges, dams, or otherstructures which lift/scrape the adhesive from the card, therebyfracturing the microcapsules and mixing the contents thereof, andredeposit the activated adhesive on the card. The sled then traverses tothe bonding station where a matching card is mated with the activatedcard at a pressure of about 5 psi applied for about 2 seconds. Thebonded card assemblies were then allowed to sit for four weeks followingwhich the ultimate peel adhesion and ultimate shear adhesion of eachwere determined. Tests were performed on five assemblies of eachadhesive system and the results averaged and presented on Table 9.

Peel Adhesion and Shear Adhesion tests were performed under Tappiconditions using a Thwing-Albert EJA materials Tensile Tester with a 200pound load cell. Instrument settings were as follows: test speed—12inches per minute, sensitivity—0.5 pounds and gage length—1.75 inches.For testing, each sample was placed in a clamp, a modified vise grip,whose jaws extended the length of the card and overlayed the bond area,parallel to the bond, so as to stabilize the bond area prior to testing.The clamp was tensioned to provide an interference fit, but not pressureon the bondline. The clamped assemblies were then folded to prepare tothe specific tests as follows:

Peel Test: For conducting the peel test, the exposed, unbonded “flaps”of the assembled cards extending from the clamp were folded back alongthe clamp edge, in opposite directions, and 90° to the assembled card inthe clamp. An end view of the so folded card would give the image of a“T”. The assembly is then centered in the jaws of the tensile tester,with each flap in opposing jaws. The assembly was then ready fortesting.

Shear Test: For conducting the shear test, a corner of one of theexposed, unbonded “flaps” of the assembled cards was dog-eared andfolded 90° to the card assembly: this produced a triangular dog ear onthe card. A similar dog ear was then formed on the other card at theopposite end of the card assembly with that dog ear extending 90° to thecard assembly, in the opposite direction of the first dog ear. Each jawof the tensile tester was then attached to one of the dog ears. Theassembly was then ready for testing.

TABLE 8 UV Curable Binder Systems Binder L M N O P Q R Sarcure SR11357.5 7.5 7.5 7.5 7.5 7.5 15 Norsolene A-110 40 40 40 40 40 40 BDDA 5 EEEA10 SA 35 26 28 5 27 5 TMPTA 5 PPGMMA 10 10 10 HDDA 9 7 8 PETA IBA 15 1530 CLA 5 CN2404 oligomer 20 15 15 15 CN551 25 25 CN501 20 Jayflex DIOP10 10 CYM M-100 5 Indopol H-100 10 Wingtak 10 10 glyceryl tribenzoate7.5 Norpar 12 7.5

TABLE 9 Examples 29–36 Example Composition 29 30 31 32 33 34 35 36 UVBinder L 43 43 43 UV Binder M 43 UV Binder N 43 UV Binder O 43 UV BinderP 43 UV Binder Q 43 ECS Cap 5 37 32 37 37 37 ECS Cap 7 37 ECS Cap 16 32ECS Cap 18 37 ECC Cap D 20 ECC Cap E 20 ECC Cap F 25 ECC Cap G 20 25 ECCCap G ECC Cap H 20 ECC Cap I 25 ECC Cap J 20 Peel 4.4 4.4 3.5 3.5 3.744.9 3.5 4.9 Adhesion (lbs) Shear 101.1 93.4 46 87.5 50.6 70.7 45.3 48.7Adhesion (lbs)

EXAMPLE 37

A final pre-applied composition was prepared to demonstrate the efficacyof the compositions of the present invention in thread lockingapplications. In this case, a composition was prepared using 23 parts byweight of UV Binder R from Table 8, 20 parts by weight of ECCmicrocapsule K from table 7 and 57 parts by weight of the encapsulatedcure system of Example 19.

In order to test the efficacy of these compositions a 0.5″ widecircumferential band of the adhesive composition was applied to thethreads of a plurality of ½″ long, ¼″ diameter bolts. The coating wascured under UV light. Nuts were then threaded onto the bolts by handuntil the nut advanced to the upper edge of the adhesive band. Theassemblies were then allowed to set for several hours after whichefforts to remove the nuts by hand were unsuccessful. Though the actualbond strengths were not measured, it is clear that the adhesivecomposition cured and formed an effective bond.

While the present invention has been described with respect toaforementioned specific embodiments and examples, it should beappreciated that other embodiments utilizing the concept of the presentinvention are possible without departing from the scope of theinvention. The present invention is defined by the claimed elements andany and all modifications, variations, or equivalents that fall withinthe spirit and scope of the underlying principles embraced or embodiedthereby.

We claim:
 1. An encapsulated cure system for curable compositionscomprising: a) an in-situ formed carrier material, b) a curativecontained in said carrier material, and c) a polymer capsule encasingsaid carrier material; wherein the in-situ formed carrier material is anatural or synthetic material or composition that is substantiallynon-flowing in the absence of external forces, elevated temperatures orboth and is formed by the action of a curative with or on a precursorcomposition for said carrier material following the addition of thecurative (b) to said precursor composition wherein either (i) thecurative for the in-situ formed carrier material is different from andin addition to the curative (b) contained in said carrier material or(ii) the curative for the in-situ polymerized carrier material is thesame as the curative (b) and the amount of said curative is at least 1.6weight percent prior to the in-situ polymerization of the carriermaterial and at least 0.1 weight percent following the in-situpolymerization of the carrier material: weight percent being based onthe weight of the carrier material, said curative for the carrierprecursor composition being soluble or miscible in said precursorcomposition.
 2. The encapsulated cure system of claim 1 wherein thecarrier material is (a) of a soft, putty-like or gel-like character or(b) a solid or semi-solid that is (i) soluble in a liquid curable matrixcomponent of the curable composition with which they are to be used,(ii) softened by a liquid curable matrix component of the curablecomposition with which they are to be used, (iii) softened by thereaction conditions under which the curable composition with which theyare to be used is cured or polymerized, (iv) softened by theenvironmental conditions under which the curable composition with whichthey are to be used is cured or polymerized, (v) is softened by themethod or process by which the curative (b) is to be made available toother components of the curable composition with which they are to beused, (vi) rendered flowable by a liquid curable matrix component of thecurable composition with which they are to be used, (vii) renderedflowable by the reaction conditions under which the curable compositionwith which they are to be used is cured or polymerized, (viii) renderedflowable by the environmental conditions under which the curablecomposition is cured or polymerized, (ix) is rendered flowable by themethod or process by which the curative (b) is to be made available toother components of the curable composition with which they are to beused.
 3. The encapsulated cure system of claim 2 wherein the carriermaterial is of a soft putty-like or gel-like character and the precursorcomposition comprises a thixotropic or thickened composition ofmonomers, oligomers or pre-polymers, or a combination thereof, whichcomposition is substantially non-reactive with the curative (b) in theencapsulated state.
 4. The encapsulated cure system of claim 3 whereinthe carrier material includes or comprises one or more thixotropicagents or one or more thixotropic or non-thixotropic gelling orthickening agents that are generated in-situ or act latently concurrentwith or following encapsulation of the carrier material.
 5. Theencapsulated cure system of claim 2 wherein the carrier material isselected from the group consisting of hot melts, pressure sensitiveadhesives, rubber materials, elastomer/tackifier compositions, a polymerwhose Tg is less than 35° C., semi-solid and solid resins, starches andstarch-based polymers, hydrogels, low temperature waxes and a thickenedor gel-like mass of one or more monomers, oligomers, prepolymers orcombinations thereof.
 6. The encapsulated cure system of claim 2 whereinthe carrier material is an adhesive or has latent adhesive properties.7. The encapsulated cure system of claim 1 wherein the carrier materialdoes not flow or deform except when subjected to forces of at least 1psi.
 8. The encapsulated cure system of claim 1 wherein the curative (b)is dispersed in the carrier.
 9. The encapsulated cure system of claim 1wherein the curative (b) is dissolved in the precursor composition. 10.The encapsulated cure system of claim 9 wherein the curative (b) and theprecursor composition are miscible with one another.
 11. Theencapsulated cure system of claim 1 wherein the capsule wall issubstantially impermeable to the curative (b).
 12. The encapsulated curesystem of claim 1 wherein the curative (b) is substantiallynon-migratory in said carrier.
 13. The encapsulated cure system of claim1 wherein the curative (b) following formation of the in-situpolymerized carrier material amounts to from about 0.1 wt. percent toabout 25 wt. percent of the carrier.
 14. The encapsulated cure system ofclaim 1 wherein the curative (b) is a cross-linking agent or hardenerand the amount of the curative is from about 2 wt. percent to about 50wt. percent of the carrier.
 15. The encapsulated cure system of claim 1wherein the polymer capsule comprises from about 0.8 wt. percent toabout 25 wt. percent of the encapsulated cure system.
 16. Theencapsulated cure system of claim 1 wherein the precursor compositioncomprises one or more polymerizable monomers, oligomers, prepolymers orcombinations thereof.
 17. An encapsulated cure system comprising a) anin-situ formed carrier material, b) a curative contained in said carriermaterial, and c) a polymer capsule encasing said carrier material;wherein the in-situ formed carrier material is a natural or syntheticmaterial or composition that is substantially non-flowing in the absenceof external forces, elevated temperatures or both, and is formedconcurrent with or subsequent to encapsulation thereof from a liquidcarrier precursor composition having mixed, dispersed or dissolvedtherein the curative (b); said in-situ formed carrier material formed bythe action of a curative with or on said liquid carrier precursorcomposition following the addition of the curative (b) to said precursorcomposition wherein either (i) the curative for the in-situ formedcarrier material is different from and in addition to the curative (b)contained in said carrier material or (ii) the curative for the in-situpolymerized carrier material is the same as the curative (b) and theamount of said curative is at least 1.6 weight percent prior to thein-situ polymerization of the carrier material and at least 0.1 weightpercent following the in-situ polymerization of the carrier material:weight percent being based on the weight of the carrier material, saidcurative for the carrier precursor composition being soluble or misciblein said precursor composition.
 18. The encapsulated cure system of claim17 wherein the curative (b) is miscible with the liquid carrierprecursor composition.
 19. The encapsulated cure system of claim 17wherein the carrier material is (a) of a soft, putty-like or gel-likecharacter or (b) a solid or semi-solid that is (i) soluble in a liquidcurable matrix component of the curable composition with which they areto be used, (ii) softened by a liquid curable matrix component of thecurable composition with which they are to be used, (iii) softened bythe reaction conditions under which the curable composition with whichthey are to be used is cured or polymerized, (iv) softened by theenvironmental conditions under which the curable composition with whichthey are to be used is cured or polymerized, (v) is softened by themethod or process by which the curative (b) is to be made available toother components of the curable composition with which they are to beused, (vi) rendered flowable by a liquid curable matrix component of thecurable composition with which they are to be used, (vii) renderedflowable by the reaction conditions under which the curable compositionwith which they are to be used is cured or polymerized, (viii) renderedflowable by the environmental conditions under which the curablecomposition with which they are to be used is cured or polymerized, (ix)is rendered flowable by the method or process by which the curative (b)is to be made available to other components of the curable compositionwith which they are to be used.
 20. The encapsulated cure system ofclaim 17 wherein the liquid carrier precursor composition comprises oneor more monomers, oligomers, prepolymers or combinations thereof which,in the absence of other curatives or conditions, is substantiallynon-reactive with the curative (b).
 21. The encapsulated cure system ofclaim 17 wherein the liquid carrier precursor composition comprises oneor more monomers, oligomers, prepolymers or combinations thereof whichis reactive with the curative (b) provided that the amount of curative(b) in the precursor composition exceeds that which is needed to effectcure or polymerization of the precursor composition.
 22. Theencapsulated cure system of claim 17 wherein the precursor compositioncomprises one or more polymerizable monomers, oligomers, prepolymers orcombinations thereof.
 23. The encapsulated cure system of claim 17wherein the curative (b) is substantially non-migratory in said carrier.24. The encapsulated cure system of claim 17 wherein the polymer capsulecomprises from about 0.8 wt. percent to about 25 wt. percent of theencapsulated cure system.
 25. A curable composition comprising one ormore liquid polymerizable monomers, oligomers, prepolymers or acombination thereof and an encapsulated cure system said encapsulatedcure system comprising: a) an in-situ formed carrier material, b) aneffective amount of a curative contained in said carrier materialsuitable for effecting cure of the aforementioned liquid polymerizablematerial, and c) a polymer capsule encasing said carrier materialwherein the in-situ formed carrier material is a natural or syntheticmaterial or composition that is substantially non-flowing in the absenceof external forces, elevated temperatures or both and is formed by theaction of a curative with or on a precursor composition for said carriermaterial following the addition of the curative (b) to said precursorcomposition wherein either (i) the curative for the in-situ formedcarrier material is different from and in addition to the curative (b)contained in said carrier material or (ii) the curative for the in-situpolymerized carrier material is the same as the curative (b) and theamount of said curative is at least 1.6 weight percent prior to thein-situ polymerization of the carrier material and at least 0.1 weightpercent following the in-situ polymerization of the carrier material:weight percent being based on the weight of the carrier material, saidcurative for the carrier precursor composition being soluble or misciblein said precursor composition.
 26. The encapsulated cure system of claim25 wherein the carrier material is (a) of a soft, putty-like or gel-likecharacter or (b) a solid or semi-solid that is (i) soluble in a liquidcurable matrix component of the curable composition with which they areto be used, (ii) softened by a liquid curable matrix component of thecurable composition with which they are to be used, (iii) softened bythe reaction conditions under which the curable composition with whichthey are to be used is cured or polymerized, (iv) softened by theenvironmental conditions under which the curable composition with whichthey are to be used is cured or polymerized, (v) is softened by themethod or process by which the curative (b) is to be made available toother components of the curable composition with which they are to beused, (vi) rendered flowable by a liquid curable matrix component of thecurable composition with which they are to be used, (vii) renderedflowable by the reaction conditions under which the curable compositionwith which they are to be used is cured or polymerized, (viii) renderedflowable by the environmental conditions under which the curablecomposition with which they are to be used is cured or polymerized, (ix)is rendered flowable by the method or process by which the curative (b)is to be made available to other components of the curable compositionwith which they are to be used.
 27. The curable composition of claim 25further comprising a thickening agent or a thixotrope so that theencapsulated curative (b) will remain suspended therein for a sufficientperiod of time to allow the applicator to finish the application of theadhesive to the whole of the parts to be bonded.
 28. The curablecomposition of claim 25 wherein the carrier material is of a softputty-like or gel-like character and the precursor composition comprisesa thixotropic or thickened composition of monomers, oligomers orpre-polymers, or a combination thereof, which composition issubstantially non-reactive with the curative (b) in the encapsulatedstate.
 29. The curable composition of claim 25 wherein the carriermaterial includes or comprises one or more thixotropic agents or one ormore thixotropic or non-thixotropic gelling or thickening agents thatare generated in-situ or act latently concurrent with or followingencapsulation of the carrier material.
 30. The curable composition ofclaim 25 wherein the carrier material is selected from the groupconsisting of hot melts, pressure sensitive adhesives, rubber materials,elastomer/tackifier compositions, a polymer whose Tg is less than 35° C,semi-solid and solid resins, starches and starch-based polymers,hydrogels, low temperature waxes and a thickened or gel-like mass of oneor more monomers, oligomers, prepolymers or combinations thereof. 31.The curable composition of claim 25 wherein the carrier material is anadhesive or has latent adhesive properties.
 32. The curable compositionof claim 25 wherein the carrier material does not flow or deform exceptwhen subjected to forces of at least 1 psi.
 33. The curable compositionof claim 25 wherein the liquid polymerizable material is selected fromthe group consisting of monomers, oligomers and/or prepolymers thatundergo vinyl polymerization; unsaturated polyesters; urethanes; epoxyresins; polysulfides; isocyanates; silicones; polyethers, polyurethanesand polyolefins having silanol moieties capable of undergoing silanolcondensation or hydrosilation reactions; and phenoxy resins.
 34. Theencapsulated cure system of claim 25 wherein the precursor compositioncomprises one or more polymerizable monomers, oligomers, prepolymers orcombinations thereof.
 35. The curable composition of claim 25 whereinthe curative (b) is substantially non-migratory in said carrier.
 36. Thecurable composition of claim 25 wherein the polymer capsule comprisesfrom about 0.8 wt. percent to about 25 wt. percent of the encapsulatedcure system.
 37. An adhesive or sealant composition that is capable ofbeing preapplied to a substrate comprising: a) an encapsulated curesystem containing a curative, the encapsulated curative, b) anencapsulated liquid curable composition, which liquid curablecomposition is capable of curing or polymerizing in the presence of theencapsulated curative, and c) a binder for adhering the encapsulatedcomponents to the substrate to which they are to be applied; wherein theencapsulated cure system comprises the aforementioned encapsulatedcurative, an in-situ formed carrier material in which the encapsulatedcurative is incorporated and a polymer capsule encasing said carriermaterial wherein the carrier material is a natural or synthetic materialor composition that is substantially non-flowing in the absence ofexternal forces, elevated temperatures or both and is formed by theaction of a curative with or on a precursor composition for said carriermaterial following the addition of the encapsulated curative to saidprecursor composition wherein either (i) the curative for the in-situformed carrier material is different from and in addition to theencapsulated curative contained in said carrier material or (ii) thecurative for the in-situ polymerized carrier material is the same as theencapsulated curative and the amount of said curative is at least 1.6weight percent prior to the in-situ polymerization of the carriermaterial and at least 0.1 weight percent following the in-situpolymerization of the carrier material: weight percent being based onthe weight of the carrier material said curative for the carrierprecursor composition being soluble or miscible in said precursorcomposition.
 38. The composition of claim 37 wherein the carriermaterial is (a) of a soft, putty-like or gel-like character or (b) asolid or semi-solid that is (i) soluble in a liquid curable matrixcomponent of the curable composition with which they are to be used,(ii) softened by a liquid curable matrix component of the curablecomposition with which they are to be used, (iii) softened by thereaction conditions under which the curable composition with which theyare to be used is cured or polymerized, (iv) softened by theenvironmental conditions under which the curable composition with whichthey are to be used is cured or polymerized, (v) is softened by themethod or process by which the encapsulated curative is to be madeavailable to other components of the curable composition with which theyare to be used, (vi) rendered flowable by a liquid curable matrixcomponent of the curable composition with which they are to be used,(vii) rendered flowable by the reaction conditions under which thecurable composition with which they are to be used is cured orpolymerized, (viii) rendered flowable by the environmental conditionsunder which the curable composition with which they are to be used iscured or polymerized, (ix) is rendered flowable by the method or processby which the encapsulated curative is to be made available to othercomponents of the curable composition with which they are to be used.39. The composition of claim 37 wherein the binder material is anadhesive or coating material in solution.
 40. The composition of claim37 wherein the binder is an aqueous based binder system.
 41. Thecomposition of claim 37 wherein the binder material is an actinicradiation curable composition.
 42. The composition of claim 37 whereinthe carrier material is of a soft putty-like or gel-like character andthe precursor composition comprises a thixotropic or thickenedcomposition of monomers, oligomers or pre-polymers, or a combinationthereof, which composition is substantially non-reactive with theencapsulated curative in the encapsulated state.
 43. The composition ofclaim 37 wherein the carrier material includes or comprises one or morethixotropic agents or one or more thixotropic or non-thixotropic gellingor thickening agents that are generated in-situ or act latentlyconcurrent with or following encapsulation of the carrier material. 44.The composition of claim 37 wherein the carrier material is selectedfrom the group consisting of hot melts, pressure sensitive adhesives,rubber materials, elastomer/tackifier compositions, a polymer whose Tgis less than 35° C., semi-solid and solid resins, starches andstarch-based polymers, hydrogels, low temperature waxes and a thickenedor gel-like mass of one or more monomers, oligomers, prepolymers orcombinations thereof.
 45. The composition of claim 37 wherein thecarrier material is an adhesive or has latent adhesive properties. 46.The composition of claim 37 wherein the carrier material does not flowor deform except when subjected to forces of at least 1 psi.
 47. Thecomposition of claim 37 wherein the liquid curable composition isselected from the group consisting of monomers, oligomers and/orprepolymers that undergo vinyl polymerization; unsaturated polyesters;urethanes; epoxy resins; polysulfides; isocyanates; silicones;polyethers, polyurethanes and polyolefins having silanol moietiescapable of undergoing silanol condensation or hydrosilation reactions;and phenoxy resins.
 48. The encapsulated cure system of claim 37 whereinthe precursor composition comprises one or more polymerizable monomers,oligomers, prepolymers or combinations thereof.
 49. The composition ofclaim 37 wherein the curative (b) is substantially non-migratory in saidcarrier.
 50. The composition of claim 37 wherein the polymer capsulecomprises from about 0.8 wt. percent to about 25 wt. percent of theencapsulated cure system.